Longdark Creepers

The longdark swamp in winter is an impenetrable tangle of darkness and decay, where the sun does not shine for months on end. The only light then comes reflected with a blue tint from the gas giant planet in the sky, and from colorful, dancing polar auroras, both of which are often hidden behind thick cloud cover.

It is a wonderful place to hide from those you do not want to know you are there.

But a terrible place for those unlucky ones who get found.

The hidebehind is a very tall carver, a flightless sea raven descended from the joojub bird. Reaching 11 feet, it is built like a beanstalk and is exceedingly light and thin, with a weight of only 180 lbs. This means the hidebehind is fairly delicate, and so it is no fighter. It is, instead, an exceedingly sneaky, patient ambush predator. Like its precursor before it, the hidebehind moves with methodical, quiet steps and trails its victims unseen for quite some time before it strikes. It can freeze for very long periods of time. It ducks behind tree trunks with sudden bursts of speed as it closes slowly in, and if caught away from such cover, it may be seen tightening its plumage and raising its beak skyward so that its own shadowy silhouette resembles nothing more threatening than another trunk in the woods. The hunt may last hours, the hunter trailing the quarry unheard and unseen, coming just a little bit closer every time its prey turns away, for even just a moment. 

And then it makes its final move.

The hidebehind always strikes from behind, bowling its hapless victim over with a sudden powerful kick, followed instantaneously with a deadly blow from its pointed beak, aimed squarely at the brain. Animals never know what has hit them before their lights are knocked out, and only rarely does it take another hit to keep their target down. Prey as heavy as itself is subdued in an instant, and only once it is killed does the hunter at last break its vow of silence. The hidebehind throws its head back and croons a song of triumph, a drawn-out, plaintive call which resonates louder in a hollow casque on top of its sinuses before carrying far and wide across the forest. It tells rivals that this territory's owner is strong and well-fed, and warns against intruders. But it also tells a partner, hunting somewhere distant in the glades, to come and share the spoils. Hidebehinds form lifelong pair bonds, and though they hunt alone, they like to share their kills with one another during the winter, the male feeding the female tidbits of flesh from his own beak when she arrives to strengthen their bond. This is their breeding season, when large prey is easier to sneak up on, and competing predators are fewer on the ground. As winter progresses, the female settles down in a quiet reedbed or thicket of polepoa canes to brood a single large, white egg, and the male will then deliver her all the food she needs until it hatches. The chick is precocial, fuzzy, and already 20 inches high when it emerges; it leaves the nest within a day, and then stays at its parent's heels for the rest of the winter, watching them close as they hunt, learning their techniques, and instinctively keeping just as quiet. When spring comes and the forest sees its first peek of sunlight in months, the hidebehinds leave the forest for the low-lying wetlands and there spend their summers wading in the swamps, hunting fish and much smaller animals in the sunlit world where they can no longer so easily vanish into plain sight. Pairs soon split up, but just for a while, as now-independent chicks go their own ways, until the darkness returns, and these specters of the forest regroup to reaffirm old relationships, and together haunt the high ground once more.

The nightstrider is migratory an inland hellican, a monotypic genus that diverged before all other species, which migrates each year from pole to pole in reverse of the normal seasonal movements of most animals. It reaches the longdark swamp at the onset of winter, and remains there until spring, then flies nearly nonstop to the northern upperglades just before the south polar spring to experience almost total year-round winter - a pattern of behavior only seen in a few other birds, such as the antipodal prowl. Its reasoning is identical - it is a specialist nocturnal predator, and so it chooses to spend as much of its life as possible in its preferred hunting conditions, a quiet world of dim light and mystery.

Though its power of flight is strong enough to carry it across the world, the nightstrider does not typically fly at all outside migration. It usually can't - it hunts on foot, and typically in the deepest, darkest impenetrable swamps where there is no room to get lift off, or even to open their wings. The appearance of the nightstrider is at once both more and less derived than in the other hellicans - its plumage is very different, being nearly black and with a large crest absent in all others; the underside of the crest and the trailing edges of the wings are bright orange, lending the illusion that they are glowing with hot embers when planetlight hits them just right. This may be used in social display - namely, to flash these reflective feathers as a warning for others of their species to stay out of their way, as they are territorial. But the throat pouch in this species is much smaller than in others, and its use much more limited; nightstriders have proportionally longer necks but smaller jaws, too - all adaptations to a diet of small, bite-sized morsels like murds, which they usually catch by snaking their necks into tall grass and brush where their victims are hiding. Though they are huge - up to 15 feet high, and weighing hundreds of pounds - they move nearly noiselessly through the swamp with careful, delicate movements and padded toes which help to distribute their weight over the murky substrate. They are visual hunters, their pupils taking up nearly the entire space of their eye to catch all traces of light in the polar night, and they are particularly attuned to movement.

The solitary nightstrider lacks a set breeding season, and can reproduce any time of year except during the migration itself, as it ensures itself a year-round consistent environment in which food is always available for its young. Females may even breed twice yearly, once each in the northern and southern hemisphere. In contrast to the vast majority of bird species, it is the female nightstrider which sings to call in a mate; when she is receptive, which lasts for about six days, she fills the shadowed forest with a beautiful, if haunting melody that lasts as long as fifteen minutes, and may be repeated once an hour. The call attracts an entourage of males, which are slightly smaller, and which trail her for as long as she is interested in mating. Over her nearly week-long receptive period, the female accepts many different suitors to maximize the genetic diversity of her progeny, and this may be the reason she announces her interest to breed rather than having to spend time seeking out single calling males, each like a needle in a dark polar haystack.

Though the female nightstrider makes a simple nest of vegetation to brood her pupa as they are born, she provides no further care once the young hatch - as many as forty of them. Her whole brood emerges and spends less than a day in the nest before climbing out, often upon their mother, and taking flight into the darkness all alone. They are initially insectivores, bat-like creatures, and they need no further attention. When spring comes, they will follow the shadows instinctively to middle latitudes and there spend their infancy, hunting by the equatorial night and roosting away by day. Adolescents a few months old become bird-hunters, swallowing their prey whole on the wing, and flocks pose a threat to the young of other archangels such as the emperor stormorant. Nightstriders don't adopt the strongly migratory nature of their elders until they are three or four years old, by which time they are becoming more terrestrial and are no longer as skilled at catching food in flight. Because the chicks have no protection from enemies, only a very small percentage finally reach adulthood, which occurs at a very late age even among their related birds, after ten to twelve years.

As the hothouse progresses, highly intelligent, and extremely coordinated squabgoblin scroungers are greatly changing the ecology of Serinaustra, in particular by killing their competing predators. By 290 MPE, this has had two major effects on surviving, contemporary carnivores. Some have become very good at avoiding these human-like, tool-using enemies, or in remaining unseen until they can strike them by surprise and then vanish before this most dangerous of prey can retaliate. This is true for both the hidebehind and the nightstrider. 

The other category is very different. Squabgoblins are formidable opponents, but they are small animals. Past a certain size, and not even the best tools and plans of these scroungers are very effective against you. So some predators survive simply by virtue of being big - and without selective pressure to fear anything at all, these animals are often exceedingly fierce. In this category are such giants as the gigantic, deadly atrocious crossjaw, feared by squabgoblins universally. But not everything which has evolved down these lines of "too big and mean to kill" is a full-time predator. Enter the terrortoddle: a ferocious omnivorous burdle with a reputation that sends even squabgoblins running for cover.

Evolved from the dopey, docile toratoddle, terrortoddles are now 15 foot high, armored goliaths lined with knife-like serrated scutes, frightening spiked jaws, and temperaments that would rival a honey badger. Most of the time, the terrortoddle is a browser, eating the leaves of trees. But winter still comes to the longdark swamp, and the sun's departure takes those leaves with it, as trees fall dormant until the spring. The terrortoddle is well-adapted to walk upright (but can also, if it chooses, walk on all fours with their claws folded up) - but is not inclined to make long-distance migrations toward evergreen forests further north. Nor can it hibernate, like some earlier Serinaustran burdles could. So to fill its stomach in the dark season, terrortoddles become hunters. Herds that mainly kept to themselves in the summer months, flashing their sharp beaks and huge defensive claws only if threatened, now scour the forest endlessly in search of calories wherever it can get them. No longer gentle browsers, now they push over trees, shredding the wood to access huge grubs that hide deep within. They gobble mushrooms by the mouthful. And they grab and kill any animal that they corner, dismembering it in their wing claws like a monstrous praying mantis and eating it still alive. Thick protective scutes across their bodies, evolved first to protect from large predator's bites, now  defend from their victim's struggles as they feed on whatever they can, for they are the predator now. Squabgoblins are kept on the move in fear, for though they could - maybe - take on a single terror, these animals live in groups and work together, perhaps inadvertently, to trap and catch their prey. Large, but shaped narrow bodies that can slip through old-growth forests, their habitat preference lends them shelter from the only predators big enough to kill them, while they exploit the dense forest's lack of mid-sized carnivores, thanks to squabgoblin's successful onslaught against them. In removing so many of these animals over time, the scroungers have unintentionally produced a new, perhaps even scarier enemy in the form of this fierce jungle burdle, which is just small enough to threaten them even in their hiding places, and yet still big enough to find little to fear from them. Even baby terrortoddles have few reasons to fear the scroungers, for though small enough at hatching for even a single, unarmed scrounger to catch and kill, they are arboreal and grow up entirely out of reach, only returning to the forest floor when they are big enough to join the adult herds, and there find protection within.

Come spring, the leaves return, and the terrors switch back to easier-to-find fare of vegetation. In a sunlit world, would-be prey gives them a wide berth, but they now have little need to hunt. Yet even now, they may prove a menace, for an easy meal of any kind will be taken - terrortoddles are eager scavengers, and will scent out other predator's kills and take what they want. Many longdark swamp predators are now arboreal, and quickly hoist their food out of reach of the fierce adults. Squabgoblins struggle here too, however, for unable to climb, they can do little if a herd of monsters decides to take their prize. Such a significant threat has this most unlikely creature become to one of Serina's fiercest and smartest creatures, that the squabgoblin becomes warier of the thickest forests, preferring less wooded clearings where dangers can be seen from afar; in turn, other carnivores of the swamp find a reprieve from their intense pressure on the ecosystem... and things begin to return to a natural balance, at least for now.