In the late hothouse, some biomes have shifted, or even been lost, as consequence of changes in the plant and animal life upon the world. Many of the grasslands that were once the dominant habitat type worldwide have now been replaced by different types of forests. At the top of the world upon the arctic plateau now can be found one of them: the nightforest. The nightforest is an upland woodland that occurs over this elevated land region, along the western shore of the polar basin and surrounded by the upperglades - a northerly continent-wide band of interspersed soglands and floodforests associated with the polar basin, which drain into it when its levels are low, and drain out to sea when it fills. Together, these biomes are analogous to Serinaustra's longdark swamp. While all of these habitats experience prolonged winter darkness and significant seasonal changes to varying extremes, each is a unique ecoregion with a high degree of endemism. 

The night forest is a haven for myriad plants and animals which are rare in the wetter places beyond the plateau. With few exceptions, the forests here don't flood seasonally and the ground remains dry throughout the year. Conditions are more consistent and predictable than in the upperglades, and trees reach greater sizes and live longer. Like other polar vegetation, here they produce a flush of summer leaves to make the most of the sunlit summer, and then go dormant in the autumn, to sit out the polar night. Large herbivores make long travels from the south to feed and give birth, and most leave again in the autumn. Flying creatures too make annual round-trips, with some nocturnal birds even moving in the opposite way to spend almost the whole year in the dark of night. But for smaller, grounded animals, the night forest must be their home for the year-round, enduring the cooler temperatures and reduced productivity for half the year in a world of never-ending night.

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The nightforest supports the largest trees ever to exist on Serina, a giant dancing tree known as the tree-of-heaven, Scalacaelus gigas ("gigantic stairway-to-the-heavens") which can reach a maximum height of 450 feet. This height exceeds the ability of the tree to move water up to its canopy from its roots. Water is normally pulled upwards through a tree's tissues as other water evaporates in the upper leaves and produces negative pressure. The height of the tallest trees-of-heaven exceeds to length at which this is sustainable, which is somewhere around or just above 350 feet above the root system. These trees can surpass this barrier due to a few favorable conditions of their habitat which have never before occurred together, namely the proximity to the polar basin - a source of evaporation that produces clouds of water vapor which blow into the forest, and the prolonged polar winter in which atmospheric humidity approaches 100% with no water loss occurring from the tree. This allows the tree-of-heaven to grow aerial roots which are covered seasonally in fine water-wicking root hairs, letting the crown of the tree drink up water independent of the tree's primary roots, and to store huge quantities of water in its woody tissues which it relies upon to survive during the summer growing season. Still, trees of these hugest sizes can grow only along the edge of the forest which faces the polar basin and receives the greatest amount of water vapor, and the forest grows shorter significantly the further from the basin one goes until the trees rarely exceed 200 feet in height along its opposite edge.

The great height of the tree-of-heaven and other related night forest trees produces a layered ecosystem with few equivalents elsewhere, with a very dark ground floor gradually giving way to more open and sunlit levels as one moves upwards. The trees here grow in denser and wider stands than in the longdark swamp, with few lasting clearings between them. Their crowns are generally tiered, the branches staggered with clusters of leaves and then a length of bare stem before another level of foliage; this is an adaptation to catch the most of the angled polar sunlight in spring and autumn; all nightforest trees angle slightly south to further maximize the absorption of this light. These trees grow so close than even in summer their layered crowns interconnect, keeping the forest floor so far beneath in a virtually perpetual gloom of shadow, where bio-luminescent fungi and animals can flicker even in the height of summer and dangers can be lurking in the dark behind any tree. This is unlike the longdark swamp, which exhibits an open canopy and a floor that is scattered with sunlight in the summer and so can support a wider variety of plants. The tree-of-heaven dominates the nightforest far more completely, limiting the photosynthetic groundcover to the hardiest herbs that can survive the low, indirect light levels that reach it. In such an environment where it is too wet for fire to clear out adult trees periodically, it might be a mystery how the trees, though they produce vast amounts of nuts annually, manage to have any survive and grow without light. The solution, for these trees, was evolved earlier in the hothouses. Dancing trees are rare among plants in that they practice maternal care of their seedlings, whose roots link into fungal networks below ground within days of germination and from there are provided energy and nutrients from surrounding mature trees for the many years it takes them to grow tall enough to break into the sunlight. The nightforest survives despite the existence of the gigantic gantuan grazers which limit woodland coverage elsewhere as a result of millions of years of very slow growth into the dense thickets seen today, in which the oldest trees grow close enough together to effectively exclude the entry of plant-eating giants in between, allowing young trees to grow unharmed surrounded by their seniors in another example of the dancing trees' complex "sociality." The forest has taken more than five million years to reach this climax stage in which the trees can grow at such a density, and the survival of the largest adults is paramount to the ongoing survival of the biome as a whole. 

Trees as old as 50 years old will often still depend on their seniors for some of their needed sugars, making the "childhood" of this tree one of the longest of any living thing. By nourishing their own young and darkening the ground to keep any others from taking root, the trees effectively monopolize the habitat to the exclusion of other trees... at least so far as those which grow on the ground. The wet atmosphere and abundant sunlight of the canopy at the top of the forest favors the evolution of plants which grow on top of other plants and skip the race to the light entirely, and both epiphytes - which sit harmlessly on the trees' branches - and parasites, which steal their nutrients, are very numerous in the nightforest's canopy, with thousands upon thousands of endemic species, many rockroot ant trees among them.

The layers of the nightforest are each inhabited by their own specialized animal denizens, which thrive from the darkest depths of the forest floor up to the highest branches of the crown. We begin our journey into the nightforest at its bottom rung, the darkest and most secluded floor level, home to cryptic and mysterious creatures that slink and skulk through a world of eternal shadow.

The ticklemonster's body is mostly bald, and large scales are present along the featherless parts that help defend against ant stings. The back is feathered in the same sparse and unkempt way as many northern skuorcs, perhaps for insulation in the cooler winter nights to prevent heat loss as it curls up in a den. It is an integument distribution that unfortunately gives it an appearance like a diseased, mangy rat, even when it is in fact quite healthy. 

In addition to insects, ticklemonsters have another favorite food that they seek out more heavily in the summer months: birds' eggs. The same adaptations that let them hunt for ant larvae and honey work well to crack open unattended eggs and remove the contents, and the tickler is an accomplished nest raider, able to snatch an egg and run off to feed at leisure in a sheltered spot. It rounds out its diet with other odds and ends; a few green leaves, fallen nuts, a bit of fruit, and the odd small animal it can stomp with its toe claws will all be eaten occasionally - the ticklemonster is more generalistic than its specialized anatomy would lead on, and adaptable behavior lets it get by through the changing seasons and different opportunities they provide. 

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Bogglebirds are another omnivore that stalks the forest floor. A group of chatterers adapted to nocturnal lifestyles in the hothouse, they are found worldwide, especially in polar regions. With large dark eyes, and in some groups a sound-amplifying disc of feathers, they hunt for food in conditions too dim for humans to see at all, catching small animals with long pointed beaks, and sometimes also feeding on seeds and fruit. Species mostly range along a similar variety of shapes and sizes to the ancestral chatterers, from magpie- to raven-like. But the prowls are significant outliers - many bogglebirds have somewhat long legs and sometimes hunt along the ground, but prowls take it to the extreme. They are a small genus of very tall, slender sparrowgulls standing three to five and a half feet tall, which do all of their hunting on the forest floor. 

The antipodal prowl breeds in the far north in midwinter, the only bogglebird to have switched its breeding and resting seasons; whether this has occurred to prevent hybridization with southern-breeding relatives, or this change in nesting habitat led to this species becoming distinct, is unknown. While other bogglebirds breed in the longdark swamp and fly north in the spring to molt their feathers and regain their energy reserves, antipodal prowls breed in the night forest, then make the remarkable 22,000 mile flight across the world back to the south pole to spend the remainder of the year. 

Social behavior in adult prowls is based on male-female pairs, which stay together for life, but take new mates if one partner dies, with juveniles forming flocks for their first year before pairing off. Chicks are hatched in a nest averaging ten feet off the ground in the crook of a mature tree, and average two - more eggs may hatch, but the female begins sitting from the first one so that each hatches later than its older siblings and usually lose out to them competing for food. Like most sparrowgulls, prowls will carry their eggs and chicks in their wings if the nest is threatened and run away. Antipodal prowls fledge within 6 weeks of hatching and are nearly adult sized by the first light of spring, when they follow their parents south to spend the next part of the year. 

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All forests have herbivores, and this one is no exception. The nightforest of northwest Serinarcta is home to the tallest forests of the hothouse age, and a wide variety of equally large and impressive animals occur within it, making use of its food resources. But the biggest of all, the gantuans and their relatives, cannot be full-time inhabitants, and are relegated to the status of seasonal visitors, which visit the forest in the summer and browse along the margins. They are forced to leave these vast woodlands in the fall when the sun sets and the trees shed their leaves - there is simply not enough else to sustain them once the trees fall dormant and the branches fall barren. It is then that the nightforest's smaller denizens rule - and in some cases, smaller is only a relative descriptor.

Nightforest trees are unusual in that they have evolved to grow upwards during the middle of winter, when they have no leaves, by relying on energy stored during the summer. In this way their tender new branches are protected from the worst browsing, so that by the time the herds return in abundance, the new branches have hardened and put out a crop of soft leaves which will be eaten instead - and which are more easily replaced. Few trees gain height during summer, save the very tallest and oldest ones that break the canopy, as it simply isn't worth it with the high probability of damage from herbivores. So in a way, the trees trick the herbivores into leaving. When the leaves fall in the autumn twilight and it seems that the forest will become dead, most large animals leave. Only about six weeks later, when the coast is clear, do the trees awaken in the dark of night and begin a rapid winter-long growth spurt, sending out soft, pale shoots into the starlit sky. Gantuans couldn't survive the month and a half long period without leaves or new branches to eat, but there are some other animals which are just adaptable enough to do so, and so which can take advantage of this secret winter food source if they are just patient enough to wait for it. 

The male broods the egg for some five weeks and then continues to care for the chick for the next two years, courting a mate only in alternate years as a result, while females can lay a new egg every spring. Seeking help in child-care, some male tree trunks, including the forest banshee, form longer-lasting partnerships with other males with chicks and aid one another in protecting their offspring from predators. Unexpectedly, these bonds are not always between males of the same species - there is still a benefit to working together to raise their young, and no downside, whether or not two males may be exactly the same size and color. Hybrids between males and females of different species are much rarer, however, as courtship seasons often differ for each species, ranging anywhere from spring to fall. Females are not typically receptive outside a few weeks long window every year, and males are typically saddled with egg-sitting duty and so stop courting at the same time, meaning few opportunities exist for interspecies coupling which is so common in some other birds, including their ancestors. 

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The tree trunks are exceptional for their height, and most year-round nightforest residents are more modest in size. Many smaller "herbivores" are present here, animals that aren't adapted to hunt animals, and which graze on non-mobile food. But as the forest is pitch black for part of each year, and the growth of the trees often out of reach of shorter creatures, just what these animals eat varies. Many eat fungi, which thrive in the musty conditions and sometimes reach huge sizes. But some megafauna eat something that few animals of such a size can: they are specialist browsers... of dead, rotting wood. Filling a role here that is normally the domain of tiny insects and worms, the prismuffalope survives on a diet utterly indigestible to nearly all vertebrates, but not to thorngrazers.

While most herbivores vacate the high latitudes with the dimming of the light, the highly distinctive prismuffalope stays behind, even though it is too short to browse the winter growth of the trees. A large 700 lbs descendant of the battering helmethead, this crested thorngrazer can survive the dark months on food that no bird ever could: the cellulose and hemicellulose that makes up much of the structure of wood. These related organic polymers, one of the building blocks of plant tissues, are made up of glucose (sugar) molecules, but are indigestible to nearly all animal life. For most of life's history, bacteria were the primary organisms responsible for the digestion of cellulose, but thorngrazers now have the capacity, having acquired the gene to produce the cellulase enyzme to break it down through horizontal gene transfer from a symbiotic stomach bacteria, now extinct, in the mid-Ultimocene. In an environment where they can't be the biggest herbivores and are no longer the meanest, this wider range of diet now gives some the edge over avian plant-eaters. Gantuans must vacate the nightforest in the autumn, for they can only digest the softer green parts of plants, while the prismuffalope simply adopts a seasonal diet of tree bark and deadfall; logs, sticks, and dried up or rotting wood material that is completely non-nutritive to other animals. Its presence here affects the entire ecology of the region, for unlike in the longdark swamp there is very little chance for logs to accumulate, and so this type of shelter, used by many small animals in the southern hemisphere, is not nearly as available here.   

The prismuffalope's head is a powerhouse of a structure, supported by a huge muscular shoulder hump,  and lets it easily push over small trees to reach their upper branches. Its grinding jaws meanwhile are strong enough to easily pulverize dead trunks and logs to a slurry-like wood pulp. It sometimes also strips more nutritious bark by jutting its jaw tusks into the trunk, leaving deep furrows from which it can dig out a mouthful of bark and tear it away in its jaws - but the prismuffalope does not eat only wood, though in winter this is the bulk of its diet. Its summer diet favors green plants and it becomes a low browser that feeds on whole shoots, stems and all. Even in winter, it gains a significant amount of calories and nutrients by incidentally consuming the insects living in rotting wood. Only lignin is left undigested in the prismuffalope's droppings, which are dry and hard and deposited along the forest floor like piles of gravel, and so stripped of anything nutritious that they may take years to decompose.

Prismuffalopes take advantage of the lack of large predators in the nightforest in winter, spending the season widely dispersed and solitary, so that there is not enough prey concentration for most hunters to bother sticking around. Yet in summer carnivores do visit the forest, and this thorngrazer must gather into groups to breed. As males display to attract females in the early days of fall, they create a loud trumpeting call with their paired, back-swept nasal horns to attract females - but this can also draw in danger. Sawjaws, which haven't all left the woods by this time, can then more easily find the gathered prismuffalopes -  but it is difficult to kill one, for this species of thorngrazer is both long-legged and able to run at a decent clip through the dense forest, and also strong and able to defend itself well. These predators want to target the necks of their victims, but this thorngrazer's neck is short and its head is massive, making a bite there hard to accomplish. Both sexes of prismuffalopes have large bony domes over their snouts, from which radiate between 25 and 30 sweeping horns, and in males this dome spreads upward into a shield-like frill of solid bone. As their nasal crests run along the sides of the frill and are protected from impact, the prismuffalope can use it as a weapon without damaging them, ramming enemies and rival males with concussive force. Hunters cannot easily grab its hindquarters to trip it up or distract it to get in a neck bite either, for the hind leg is lined with tooth osteoderms that are razor sharp and resistant to sawjaw teeth like a set of armor; smaller defensive bony nodules are present throughout its hide, breaking the skin' surface here and there along its flanks. Unless the animal is very old or sick, it is the prismuffalope which usually wins such confrontations, as the sawjaws move on to seek easier quarry.

As male prismuffalopes court females, they use the slanted autumn sunlight to play a beautiful trick of the light. The bare skin within their crests is highly reflective and shimmers in a changing tapestry of blue, violet, gold and green. The sunlight hits it at the right angle to illuminate it in the eye-line of females for only a few weeks a year. The female is very choosy, demanding her suitors sing, dance, and fight for her favors - female mate choice has made the prismuffalope a jack of all trades. The lucky males sire offspring that will gestate through the dark of winter and be born in time for the green growth of spring. The spring sunlight mimics that of the fall, and the less fortunate males will sometimes try to court again for a few weeks then, too - but few females will be in breeding condition, only those which failed to conceive in the autumn, and those which are able to mate will give birth in the autumn at the worst time. Only a small percentage of such autumn calves will survive to see the spring.

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Fighting with fancy headgear is a trait the prismuffalope shares with many other creatures, among them one of the prismuffalope's closer relations. Spirespikes are a genus of strongly deer-like crested thorngrazers native to northern Serinarcta in the late hothouse. They are descended from the spiresprinter, a graceful animal that evolved in the early spire forests. Descendants of this species have radiated across the continent in the last ten million years, all of them being strongly tied to thickly forested habitats where they are well-adapted to hide from and outmaneuver predators. Small mouths and narrow jaws along with a relatively small gut indicate selective browsing of higher-energy foods than earlier ancestors; spirespikes are particular and fastidious, feeding on the choicest leaves, flowers, and fruit of low-growing forest shrubs and ignoring woody stems and coarser fare entirely, in very strong contrast to one of their close relatives. As a result, they rarely occur as far north where green plant food is less available. They are in fact among the most exclusively herbivorous thorngrazers, and eat very little animal food despite its higher nutrition, leaving alone even such rich snacks as unguarded birds' eggs in favor of a select few species of plants. The hothouse world is so rich in all kinds of resources that these animals simply have no pressing need to widen their diets. 

Spirespikes have evolved larger, sharply backswept nasal crests than their ancestors, from which a variable number of horns originate. Overall these crests have come to resemble antlers, and are used in the same manner in fights between males over breeding rights (they are almost absent in females.) Yet these crests also contain hollow nasal channels which amplify melodious mating calls, making them one of only a few thorngrazer groups to utilize their crests for both display and offensive purposes in equal measure. The crests have a base of solid bone, with two hollow, cartilaginous tubes running along the back below a thick layer of keratinized skin, which connect the airways to a nostril about halfway up the crest. Occasionally these nostrils are damaged in fighting, which can alter the voice of the animals and prevent them from being able to call properly and attract a mate - an unfortunate downside of using a single structure for multiple roles. Yet thorngrazers have a strong capacity for healing and regeneration of their crests, and over time even a badly broken horn can regenerate some of its original shape, though usually imperfectly. Old males almost invariably have damaged crests, which may have unusual numbers of horns and grow at odd angles, rendering their voices uneven and off-key; such individuals can still have reproductive success as a result of their great size and physical strength letting them drive away competitors which are less skilled in combat.

The sonorous spirespike of the southern nightforest and outlying regions of the upperglades is the largest member of its genus at up to 400 lbs and over 6 feet high at the head, and is also the loudest, able to produce a bell-like toll that can carry for two miles or more and which is used by males to defend a well-defined territory and to attract females. These animals are solitary for most of the year, especially in summer, and females only visit males long enough to breed before parting ways. This species favors deep, old-growth forest where its dark colors let it blend into deep shadows and avoid detection by its enemies, but may also be seen in more open wetland habitats where it may feed on water plants, especially in winter; its hooves are widely-splayed to let it walk over soggy ground without sinking. It is also migratory, gathering in loose bands for protection while moving north in the spring to take advantage of summer's flush of green vegetation and then moving hundreds of miles to the south again to avoid the prolonged darkness of the arctic circle. 

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Some nightforest species have convergently evolved similar traits despite sharing no relationship at all. Such is the case of the capricocks, small, angry forest giraffowl which fight with their own horny headgear in pursuit of mates. They have weakly-flighted juveniles that are poor dispersers, and mainly use their short, broad wings to flutter up to trees to escape predators. They are notable for the seasonal changes that occur in the male leading up to the mating season. They are vaguely goat-shaped quadrupeds with thick leg bones that become solid in adults and so resistant to injury while running over rocky and uneven terrain. While juveniles are omnivorous, adults are herbivores and feed on low browse in open woodland habitat, migrating in small herds to the far north in summer and some species persisting there year round. Most move south again in autumn, spending the winter in the southern reaches of the arctic plateau, a twilit region where the long night doesn't fully overtake the land and hardy plants can continue to grow at a very slow rate. They spend the summer feeding on leaves and fruit, but survive leaner winter months by eating young twigs, fungus, fallen nuts, and  mosses and lichens - meals too small and widely distributed to sustain far larger birds, but adequate for these deer-like creatures.  

Pronghorn capricocks, males sporting small six-spiked crowns throughout the year and females being plain and unadorned, court in the fall when they first reach their southerly wintering grounds. A change is undergone, beginning in summer and completing during the migration, as thick layers of keratin develop upon their horns and their bill casques as if normal growth has gone into overdrive - and in fact, it has. Males horns double in size in the months leading up to the rut, and develop fierce-looking hooks on both their upper and lower jaws that give them a vicious pinching bite but make it difficult for them to feed. But males in the rut hardly think of eating, and spend several weeks fighting one another for breeding rights, crashing their crests together and engaging in shoving matches of strength and endurance that turn to violent biting fights if neither backs down. 

Male capricocks will shed the extra horn growths and their bill hooks after the mating season is over, but their lack of feeding and exertion of energy takes a heavy toll on them. Many males of other species will die shortly after, having run themselves to exhaustion, and of them a lot which survive will regain their body condition only slowly, so that they may not mate again for two years. This pattern in its ancestors has led to a selection for two behaviorally and physically different male morphs in the pronghorn. Some males grow quicker and reach a larger size early in life, live through one rut, and usually die afterward. The other is smaller but less aggressive, usually losing in competition to the larger males in their first breeding season but becoming bigger in later ones and able to compete with them and outlive them due to having accumulated more energy reserves over a longer lifespan prior that prevent them from going into starvation while rutting. These two forms are the annual and perennial, and can be distinguished by their horn colors. Annual males have red horns, indicative of higher testosterone levels. Perennial ones have yellow to orange, showing lower levels of aggression but living much longer than their short-lived counterparts and so being able to get bigger than them over time to compensate. Eventually, if females develop a preference of one over the other, these two morphs may give rise to separate species. 

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Some nightforest species have evolved elaborate headgear for other purposes. In addition to the prismuffalope and spirespike which fight with their horns, crested thorngrazers are also represented by a forest-dwelling subset of the highly varied unicorn genus, which live in wooded habitats rather than sheer cliffs and whose hollow horns are strictly used to produce vocalizations. Close relatives of the skyland unicorn that clings to the mountainous bases of ancient cementree colonies, forest unicorns have longer legs and spend their lives on more level terrain, browsing low tree branches and undergrowth. They have less complex horns than the cliff unicorns which are not as tightly spiraled; in the equinox, they are only slightly asymmetrical and just barely rotated together. Because there are more predators on the ground equinox are more strongly social, larger, and more aggressive than species which live on sheer slopes. Males, with their larger horns, defend small harems of females from other males as well as small predators with powerful kicks and bites. 

The equinox is faster than it is strong, however, and will still flee when possible, able to dash through the shadowy forests it dwells in over northern Serinarcta with great rapidity thanks to its acute eyesight that helps it avoid obstacles in the dark. It has large eyes and its pupils widen into black circles that almost totally obscure its iris in low light conditions, narrowing to horizontal slits in the sun. Because equinox live in the far north and experience polar winter, they have evolved much better night sight than color vision, and can no longer perceive red or green. They are thus not as colorful as some others, being mostly black with white contrasting stripes on their legs and underside, with a white crest that resembles a crescent moon from some angles. Foals, meanwhile, are marked with boldly contrasted black and white spots that hide them in dappled light as their mothers leave them hidden away in thickets to feed before they are strong enough to keep up.

The varied calls of the equinox are distinctly bird-like, bubbly but eerie, similar in many ways to an owl or a loon. This unicorn has especially large ears to pick up distant calls in the forest as well as to detect approaching predators. Both sexes are crested, though males have larger horns and can produce deeper calls as a result. When alarmed the equinox emits a harsh whinny-like alarm call that serves to alert all others around of the danger. And sometimes, that danger can come from their own close relatives, for the nightforest is home to some of Serina's rarest examples of evolutionary oddities: predatory thorngrazers.

Most unicorns are prey. They may be hard to catch by choice of steep habitat, and so have few predators, or aggressive when confronted, but they all run from something and eat mostly plants. The nightmare, though, is a stark outlier in its genus. It is a predatory, albeit not completely carnivorous forest unicorn, with a diet of at least 50% meat. A denizen of the night forest, it spends sunlit summers grazing on leaves and grasses like its relatives. But when the dark comes and the trees lose their leaves, it doesn't head south like the gantuan herds or content itself to scrape by through the winter eating dead vegetation and fungi like the equinox.  It turns its sights to the other, smaller animals that too stay through the long dark season, and it becomes a killer. 

Nightmares fall into the same genus as all other unicorns - despite their differences, they are all close genetic relatives - but have several adaptations unique to them which help them to hunt. They have two fang-like tusks that jut down on either side of their upper jaw, allowing them to bite prey more effectively and hold on as it struggles. The front dewclaws are sharply hooked and used to restrain larger animals as it bites, so that it bears weight on only two hoofed toes at all times. Animals taken in winter include snoots, wumpos, loopalopes and other unicorns, especially their young; in summer, though it feeds mostly on greenery and becomes more wary to avoid other predators that arrive then, it often consumes bird's nests and may still take newborn herd animals. In summer the nightmare lives in small, temporary herds and this is when they mate, courting with noisy whistling calls. In winter they become solitary and hard to find, skulking alone in the shadows and making nearly no noise so as not to alert potential prey of their presence. 

The stomach of the nightmare is little-changed from the ice age thorngrazers' super-generalized one and has both a plant-fermenting chamber and a bypass for meat, the latter of which is reduced or absent in many other crested thorngrazers, but not in unicorns. The retention of this specialized gut means that even less derived species can still digest and make use of flesh, even though they less frequently take it if only because they live in places with a more steady supply of plants. Equinoxes supplement winter diets with insects that they root out of rotten wood, while cliff unicorns occasionally kill small animals like birds opportunistically. The active hunting tendencies of the nightmare did not appear out of nowhere, merely representing exaggerations of ancestral behavior common to their genus, and the high behavioral flexibility this thorngrazer genus is capable of that now render them one of the most successful of all.

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Another fierce hunter of the lower levels of the nightforest, but one which can also ascend into the low branches above, is a vicious-looking, flightless bird known as the ruffed rasp. It is a member of a small genus of carnivorous taptrackers, descended from the hookhead rasp, which have lost their powers of flight as they have grown in size, though they remain strong flyers earlier in their lives. Standing three to four feet high on two legs, these heavily-muscled birds are far too large to take flight without a wing-powered push as true quadrupeds can accomplish, weighing as much as 100 pounds, and so lose their flight feathers near adulthood, retaining only short coverts. They cannot push with their wings, lacking the musculature to allow them to stand on all fours, but they can pull, and so using gravity in their favor, they get around with ease by climbing, using their hooked wing claws to grapple up and down the trunks of the forest and to catch a hold from one branch to another with athletic vaulting leaps. 

Though different species vary in behavior, ruffed rasps are the most aggressive predators, and their beaks and tongues show the most specialization to dismember large vertebrate prey. Their skull is large relative to the body, and the beak is sharply hooked; bill serrations along the upper joint of the mandible serve as large slicing teeth, and they match up with similar blade-like hooks on the upper surface of the tongue to perform a shearing, chewing movement to cut meat. This species is less arboreal than its relatives due to its huge size, and descends to the ground frequently and there walks bipedally, defending itself with its sharp wing claws and vicious bite as well as a rattling warning hiss; if under duress, the ruffed rasp can also vomit up an oily and foul-smelling defensive liquid from its stomach and shoot it several feet into the face of an enemy, irritating their eyes and mucous membranes. It hunts often by ambushing prey from a low perch and dropping atop its victim; thorngrazer calves, trunkos, and young gantuans are common targets captured this way, and they are killed either as the nostrils are pinched shut with the beak from above, or the airways are punctured by the curved thumb claws from behind. The predator keeps them restrained through their death throes against the ground with its talons while perched upon their back, and once complete, usually pulls the carcass into a tree to feed out of reach of terrestrial competitors. It feeds by twisting victims apart with the wing claws and scraping out the innards and soft muscle with its prehensile tongue. 

At the southern edge of the nightforest on the upland plain, a ruffed rasp hunts an especially big prey - an equinox. Its tactic? Let gravity do the brunt of the work. Having lain in wait, concealed in shadow and vegetation high up a tree trunk, now launches itself suddenly away from its perch. In an instant its ambush will succeed, its prey thrown to the ground and gripped in a deadly grasp without ever knowing it was in danger. The hunter will restrain it and tear out its throat, and then work to dismember the carcass as quickly as possible, hoisting it limb by limb into its treetop refuge before stronger competitors arrive on the scene.

Adult rasps are solitary and territorial, avoiding one another except to mate, though the volant juveniles that still closely resemble earlier ancestors may forage in small flocks. The life cycle of this branch of skewers is exceptionally strange and derived, with the animal transforming significantly as it ages up into new niches that culminate in the arboreal adult. Many taptrackers of the late hothouse have parasitic larvae, and those of the northern Serinarctan rasps are the largest of all, for they are flesh-eating endoparasites of immense vertebrates - most often cygnosaurs and other giant skuorcs. Adult females have learned that the easiest food source for their larvae is directly at the source, and have abandoned all parental care. Now they lay their eggs in narrow, deep bite wounds inflicted into the skin of these gigantic hosts via the beak and tongue in the autumn, shortly before they leave the forest and migrate south for the winter. To do this, they seek out passing herds as they pass nearby to trees and drop down onto their backs, often unnoticed. Individual eggs just a couple centimeters across hatch in the muscle of the host, an environment warm, damp and full of rich food, and there develop over the next four to six months. They burrow through the muscle tissue a few inches below the skin, sometimes leaving molehill-like scars where they have been, before eventually forming a pupa while still inside the animal's flesh once they reach a weight of several pounds. The flighted juvenile bird emerges the following summer after the herds have returned to the forest, an unassuming woodpecker-like animal very much like its early ancestors. The young of some rasps give no indication of its origins, being benign insectivores that feed along the bark of the trees early in life. But the young of the ruffed rasp shares its parents' bloodlust. They feed on the cygnosaurs even after pupation, picking blood-sucking parasites from their bodies. For this reason they are tolerated, yet they are not really beneficial, as they quickly develop a taste for red meat as they grow and expand open wounds to prevent healing by stripping the flesh from their edges, and later become full on parasites themselves by biting new wounds into the hide. Before eventually losing their flight with increasing body size, weak flying subadults frequently congregate around carcasses like vultures to scavenge kills made by other animals and begin hunting small game on their own, which is sighted from a perch and pursued in a descending glide to be caught in the talons. Territorial behavior only develops once the flight feathers are lost entirely, which can take as long as eight years. The flocks by then disperse and establish territories in the forest that will be large enough to sustain themselves as they reach their full size.

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Living further up the trees still live other taptrackers whose evolutionary history has taken them almost as far from the ruffed rasp as can be imagined, the scarlettail taptracker. Now utterly tiny birds that feed on insects, it is hard to believe that they share an ancestor living just ten million years before. They are adapted to hunt wood-boring insects just below the bark of trees, by climbing up and down the trunks and tapping their upper beaks on the surface to listen for the hollow echos produced by grubs moving in tunnels beneath - behaviors that juvenile ruffed rasps, and the adult of one species, still partake in at a larger scale. Taptrackers are found worldwide, with their greatest diversity in polar regions, as they - like most skewers - have many adaptations for a nocturnal lifestyle. In the way they hunt, they have convergently evolved similar foraging behaviors to some scroungers and to the chiselers, the arboreal ancestors of sawjaws. The upper beak of most small taptrackers can rotate 45 degrees to either side in addition to the common up and down movement of the joint, allowing the bird to lower its chin to the bark to pick up vibrations as it knocks on the tree with its beak in a roughly circular pattern to detect the empty pockets left by feeding insects otherwise invisible. When the echos betray the hiding place of a plump grub, the skewer triangulates its location with more rapid and energetic knocking before puncturing through the bark with its stabbing mandible and pulling its prize out of the hole with surgical precision. 

It spends its first 90 days or so here before reaching a large enough size to pupate and emerge as a winged juvenile which reaches full maturity in another few months. This reproductive strategy frees the female to lay many more eggs, as she doesn't need to provide for any of them, but there are trade-offs, too. Mortality of the young is much higher than in the larger skewers that guard their larvae, and may even come from adults of the same species that will indiscriminately eat them if they catch them, just as they would the larvae of the beetles they usually hunt. They may also fall victim to the flying skurrel, another species of skuossom that feeds somewhat similarly to the taptrackers, and has even converged - as much as it could - upon their freedom of movement from tree to tree by becoming a glider. 

Insects are caught as they climb over the trees or dug out of loose bark with the claws, and sap is sometimes also eaten if it can be accessed in this way, though the skurrel has no specialized abilities to acquire it. The jaws of the skurrel are weak, unsuited to feed on vertebrate prey except for small larval metamorph birds, but its long bill is well-adapted to probe into crevices and snatch hiding prey. Like some earth birds, the muscles that power its jaws work stronger when opening rather than closing the bill, an adaptation to let it pry small holes wider to reach food hiding within. But if the skurrel is not wary, it may find itself on the menu for larger animals that also stalk the middle levels of the nightforest. For the flying skurrel, the dark of night is a comfort - a cloak of seclusion and relative safety, with the hunters of the summer gone to southern wintering grounds, and the forest that much safer. They emerge only in the polar night, spending the sunlit summer hibernating deep in dark tree holes where the light doesn't reach, and so this world of shadow and secrecy is all they know. 

But when summer ends, and the skurrels begin awakening in the dawn of darkness, others lie in wait. For a youngster waking from his first hibernation, this will be his first - and last - morning. Not all the predators have gone away - one has been waiting patient for this very moment. No sooner had the curious creature took three steps from its den did death come from above. With a plaintive shriek, the skurrel's short life came to a quick end on the barbed edge of the bill of the dire daggerbill, which flutters weakly to another tree trunk to land. It clings to the bark with its hooked talons and an additional claw on each wing, and there it folds its lance-like upper bill downwards, lowering its skewered victim against its rasping tongue to be neatly flayed apart.

Daggerbills practice parental care similar to early taptrackers, which involves larders of carrion in which the larva initially develop and later feed on within a nest, usually a tree hollow in this group. Several daggerbills practice food caching, surplus killing when food is most available and storing it on broken-off tree branches like a shrike. This is an important aspect of courtship in the massive and formidable dire daggerbill, the male of which must amass a collection of as many prey animals as he can to attract a female's attention. If he is considered a good provider, she will mate with him and then empty his display to fill her nests so that their future offspring will be well fed. 

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A little higher up in the trees still, the flying skurrel faces another foe. The beautiful but rarely seen twilynx is a highly arboreal, relatively solitary descendant of the springheel that moved into the forest as the habitat composition of northern Serinarcta changed with the evolution of different large herbivores, reducing the extent of the wide open grassland. The twilynx, though still exhibiting the specialized bipedal stance of the sawjaw lineage with its shoulders at its center of balance, now spends most of its time climbing tripedally in a similar way to its more ancient chiseler ancestors. It stalks other treetop denizens - abundant birds and squirrel-like molodonts - catching them with a swift swing of its clawed tail from above, or in its short, narrow jaws. It occasionally drops upon larger prey from a height and grapples it into submission with its fierce hand claws and double sickles, dual-purpose weapons that are now just as often used as picks to dig into to the bark of the trees for traction. 

The twilynx, as a polar species, lives in two worlds as the forest alternates through the long summer and polar night, and varies its habits with the seasons. In winter it lives high in the trees and rarely descends, while in summer it often hunts nearer to the ground under the canopy where it can still find dark hiding places to lie in wait to ambush its quarry. Dappled and blotched brown coats hide them here in a land of brown and black branches and shadows, with far northern populations trending toward a high rate of melanism - fully black fur is the best camouflage where winters are longest. Unlike some other animals, though, a twilynx can only have one coat color, and does not change with the season.

Unlike most sawjaws, the twilynx lives alone throughout much of it adult life, and finds contentment in its solitude. The small, arboreal prey they target is simply not present in great enough numbers through in the winter to support a pack of such predators in a small area, and so they must split up. Individuals defend treetop territories which are marked with obvious scratches in the bark that carry each animal's scent. Yet come the first light of spring, the twilynx briefly mingle; territorial boundaries dissolve as everyone descends to lower heights. Pairs form and mate, and relatives may meet and exchange social grooming. By midsummer females have gone their own ways again to give birth, leaving loose bands of males that may cooperate to hunt the increase in summer food. As days shorten with the fall, however, even these bands must break up and territories are re-affirmed as each individual reclaims its familiar treetop to spend the winter. With only itself to worry for, each individual spaced out across the forest in this way makes the best use of small and widely-distributed prey species available at this time of year. 

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As one ascends into the canopy of the nightforest, sunlight becomes more available, and the darkness that permeates the lower levels year-round is temporarily lifted in the bright summer months. This is the most productive zone of the habitat, where the trees produce abundant crops of nuts, epiphytic flowers bloom, and life flourishes, the dangerous world below a bogeyman they may know of, but are fortunate to rarely experience. This is where colorful birds such as scarreots, more benign seed-eating relatives of rasps and daggerbills, make their homes. It is also the home of another colorful flickbill, the red rasp, a retiring species which is also far less feared than its low-level cousin.

Over 350 feet above the ground, the red rasp (Tentaculinguis lacerynchus - ripping-beaked tentacle-tongue) rests on its perch and surveys its surroundings with half-lidded eyes. This is its element, a world that might as well be a million miles from the land so far below, and one in which few creatures ever touch the ground. This was a place colored a thousand shades of green just a few weeks ago, and the trees soaked up a shower of continuous sunlight. Now though, they shimmer yellow and gold as their leaves break free on the wind. Night is coming with the autumn, and soon even the highest reaches of these ancient woods will be draped in shadow and mystery. 

Though they look highly sinister, with their black and red plumage and a long, sharply hooked tongue that slithers in and out of a hole below their skulls, red rasps are much less aggressive than ruffed rasps and spend much of their time at rest, laying sedate along horizontal branches and surveying their treetop vista. The vast majority of their diet is still invertebrates, and they mostly feed on large, wood-dwelling insect larvae which they dig out of tree bark with their hooked, tearing bills that are smaller than those of their relative. Insects are pried out of crevices with a bizarre tongue, longer and more flexible than the ruffed rasp. Less adapted to chew flesh, it is instead capable of stretching more than 2 feet outside the mouth cavity, and able to wrap around prey and pull it out like the tentacle of a squid to pull hapless bugs down into its mouth, which opens as a hole below its head. Yet there is some reason to still be cautious around the rasp even if you are bigger than a grub - it is an occasional predator when opportunity allows. Though it cannot hunt anything close to its own size, let alone larger, it can still gruesomely dismember smaller vertebrate animals that it corners in their tree hollow dens and remove their innards in the same manner, leaving the hollowed-out corpses along the branches for flying scavengers to pick at. Such predation peaks in the end of winter, when the insects have often pupated and assumed their flying adult forms, leaving their normal supply of food relatively scarce - and coinciding with the period in which many smaller animals are in hibernation, and so easily killed. 

Thee two northern rasp species are very recently diverged from one another and broadly similar in appearance other than the longer neck feathers of the ruffed rasp, but red rasps are at least 30% smaller, and average just 70 pounds. Red rasps and ruffed rasps occur over most of the same range, but their life histories differ markedly. The former live higher in the trees, while the latter dwell from the forest floor to heights of around 60 feet up in the understory. The ruffed rasp is both more robust and much more aggressive, and prevents its relative from spending much time in the lower levels of the forest, driving it upwards with violent territorial behavior whenever the two meet, where it often takes shelter on branches that are not stable enough to support their larger rival, which is not as skilled a climber. Ruffed rasps will kill red rasps if they catch them 99% of the time; however, hybridization occurs at a very low level, virtually always between males of the larger species and a smaller female red rasp. Hybrids are fertile and intermediate in all respects between their parent species, even developing a small mane. They are able to subsist on a variety of food, though favoring small vertebrates like molmos over either small insects or large land animals. But these crosses are less powerful than the ruffed rasp, while being less agile than the red rasp, which leaves them vulnerable to attack by the former species. This is often the cause of an early death in the hybrid form, which would otherwise seem to have few disadvantages compared to its parents. 

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As we reach at last the very top of the nightforest, leaping over the thinnest branches below the open sky, live the final creatures we meet on this particular trek. Small and unassuming, but both uniquely adapted and unlike most of their relatives, these animals make their home in the crowns of the forest.

Stoatshrikes are among the most efficient, ruthless killers among the gravedigger lineage. Distinct for their unfused spinal vertebrae that gives them an almost snake-like flexibility to chase small burrowing prey underground, these weasel-like birds are fast and reactive, able to outmaneuver their victims and kill them with a deadly bite to the neck. Despite their ferocity, however, many species of stoatshrike are very cute, and their gregarious behavior - they are often much more social than other gravediggers - also increases their appeal. But as specialists of hunting burrowing prey, what could such an animal possibly be doing up at this height?

Finchworms are some of the smallest gravediggers, most weighing just a couple of pounds, and they are probably the sweetest-looking of them all with bright eyes, short beaks, and brightly colored summer plumage. They are also the most specialized as far as their flexibility, with some species having twice as many vertebrae in their backs as the ancestral gravediggers, and the most of any non-metamorphic bird. Their common name comes from their locomotion; they are highly arboreal and climb in the manner of inchworm caterpillars, hauling themselves up with their strong, short forearms and then arcing their bodies to pull the hindquarters up to meet the front legs, repeating as they ascend a tree. 

Like all stoatshrikes, these little creatures are still skilled predators, using their worm-like shapes to slip into narrow tree holes and murder all manner of equally cute and cuddly creatures for food, especially seedsnatchers. But finchworms are also omnivorous, and in summer especially reduce their hunting significantly as they seek out easier food: abundant fruit, which is rich in sugar and can maintain their high metabolic rates for less expenditure of energy than hunting. The little frugivorous finchworm, scarcely 12 inches long, may stop hunting altogether in the long sunlit days of summer as it gorges on berries and seeds, growing fat on carbs and making little effort to hide itself from prey species, which will feed right alongside it - but always keep a wary eye upon it. A very social bird, this finchworm lives in family groups which cooperatively dry and store the summer crop of fruit so it may last into the winter season. But once the sun sets and the trees go to rest, even this sweetest of gravediggers must return to its ancestral ways. When the fruits are gone, the finchworm returns to flesh to survive. It molts its vibrant summer coat and becomes a solid dark brown to hide in the shadows, and now mercilessly takes out the very same molodonts that it may have spent the sunnier months blissfully sharing in the spoils of summer with. It isn't personal to the finchworm - it's just how it must be. Taking advantage of the best hunting in the dark times and of easier sources of calories in the summer, these gravediggers make the most of their varying, seasonal world. 

The last animal of our expedition is another frugivore of the canopy, and one whose young may sometimes fall victim to the finchworm, is the red molmo. Part of a group of highly arboreal seedsnatchers that are intelligent and known for the propensity of most species for constructing complex communal nests. These molodonts have distinctive beaked faces, with teeth that cannot be fully covered by the lips and project from their snouts as a bird-like bill. Molmos have weaker upper jaws than other molodonts and feed in a modified way by plucking fruit and other softer foods from branches more like a bird than a tribbet, opening both upper and lower jaws to do so. The upper tooth rotates backward only a few degrees, enough to help smash down food enough to swallow, but not enough to crack open large seeds. Molmos are more or less specialized to eat soft foods; in addition to fruit - their primary diet - they consume some insects, leaves, and occasionally bird's eggs. Their teeth grow at a slower rate than other molodonts because they don't typically gnaw, and are generally less robust; they are easily kept in shape by rubbing against tree bark and would be damaged through frequent attempts to eat the typical food of other seedsnatchers, including the acorn-like seeds of the tree-of-heaven itself. Rather than eat the seeds of these trees, molmos forage on the fruits of their accompanying epiphytes, and so must search widely for isolated patches of suitable food plants among the monoculture of larger trees. 

The red molmo, at up to 22 pounds, is one of the larger species that exists, and is a denizen of the canopy of the southern night forest where it makes some of the most elaborate natural structures among Serinan animals. Very gregarious, the red molmo lives in clans of dozens which live in close-grouped nests that are constructed by weaving twigs together into a large, rounded, suspended basket hung up to 10 feet below a branch on a braided vine. This nest is large enough for several individuals - usually a pair and their young - to curl up to sleep, and the nest will sway if any sort of predator attempts to climb down the rope to access it, giving the family warning to jump out and flee onto the tree. Communities of red molmos will suspend their nests in great aggregations from suitable high branches so that they are accessible to one another as they leap from one to the next, but all are hung far enough below their supporting branch that predators can't easily reach them. Many eyes work together to spot danger and collectively defend their shared home; a group of nests hung close together by members of the same clan is known as a village. Red molmos are diurnal and more vulnerable in the dark, which limits their range to the southernmost edge of the night forest habitat that does not experience prolonged polar winter. With most of their predators being nocturnal, molmos will go to significant lengths to protect their nests while they sleep, and weaving bundles of large, dangerous thorns into their ropes is common to discourage carnivores from climbing down them; dummy nests are also constructed in numbers, sometimes even outnumbering inhabited nests, which can make particularly persistent predators believe that the colony is actually abandoned. These fake nests may even be booby-trapped - hunters reaching an arm or jaws inside might find themselves covered in a devastatingly sticky bundle of tree resin that will take days to groom out of their pelage.  

Molmos are very intelligent molodonts; they have the largest brain to body ratios among them. This allows them to adapt their behavior and learn new skills to survive when innate instincts would not suffice. They learn socially, both through observation and direct instruction from older individuals while young, though their ability to master a new skill is very limited after a couple years of age. Red molmos are a very non-aggressive species that does not typically even defend a territory from unrelated clans; instead, individuals may come and go so that groups often mix freely, promoting great genetic diversity. Social bonds are strengthened through mutual preening and resource sharing; conflicts are most often resolved through minor squabbles that quickly give way to reconciliatory gestures. Food is rarely scarce in the verdant forest they live in, and the species is socially monogamous but sexually promiscuous so that there is little mate-guarding behavior or competition to breed. Any male can sire young with any female, and this encourages cooperative behavior among all adults in the clan to help provide for all offspring. Not all molmos are so peaceful, however, as social structures vary greatly between even close relatives; other species may be matriarchal, patriarchal, or - rarely - mostly solitary, with varying degrees of tolerance for individuals outside their immediate family.

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