Jazz Harmony
The First Inversion Diminished Ascending—or, as they are unflatteringly known on the Homeworld, the Miser Crabs—have been around as a civilized people for two million years, thirteen million if you go by their timescale. They have spread to sixty star systems across the galaxy, and on countless more have they established trading posts, seeking the best that the universe has to offer for the lowest possible price. Their mellifluous languages, based on the manipulation of musical notes through their two larynxes, are common across all worlds with some sort of warp ability. But their own home-world, Third Inversion Dominant Ascending (in Galactic Demotic known as Jazz Harmony), holds a special place in their lung-hearts.
The System
The star, which they call Second Inversion Minor Descending (but which most other races have named some equivalent of Hephaestus), is an M-class red dwarf at 11.34 light-years away from Ajjamah's trinary system. At only 0.18 times the mass of Sol or Demeter, it has an absolute magnitude of 9.81 (for comparison, that of Sol is 4.83), but from the surface of Jazz Harmony is -26.7 (Sol's is about -26.74 from Earth), meaning Hephaestus appears about as bright as Sol in the daytime sky—but much, much bigger, being (at 1.7º) over three times Sol's angular diameter. Hephaestus is by far an older star as well—9.12 billion Earth years old—but life here hasn't actually been around that much longer, thanks to the strong bursts of radiation from Hephaestus in the first few billion years of its existence.
Jazz Harmony is the closest planet, at 0.07 AU.
The next planet out, which was terraformed over two million years ago, is locally called Second Inversion Major Seventh Ascending, but more properly may be called Pallas. Pallas is larger and colder than Jazz Harmony, but also brighter due to the thick, cloudy atmosphere which hasn't quite faded away over the aeons. Less so now, in fact, when an artificial sun provides power, tidal forces, and a magnetic field all in one. (Normally it varies between the mean brightness of Venus and the maximum brightness of Mars.) Ironically, despite its increase in size and ridiculously short day (not even fifty-five hours long, how's a person supposed to sleep?), Pallas' gravity is practically identical to that of Jazz Harmony, and today boasts a much higher population.
The next planet out is cold and icy as well—the world of Third Inversion Minor Seventh Descending, also called Zelos. Zelos, however, is past the frost-line; it is an ice ball, and as such appears as a bright blue world in the nighttime sky from Jazz Harmony. Unlike Pallas and Jazz Harmony, Zelos has two moons, Kratos and Bia.
Immediately out from Zelos is an asteroid belt. Miser Crab terraships have inhabited this region for quite some time; some ships are over a million years old, and have evolved their own unique ecology.
Beyond the asteroid belt is the system's only gas giant, Root Minor Ascending, also called Phosphora. A green world shining as bright as Pallas in the night sky of Jazz Harmony, Phosphora has multiple moons, six of which have been colonized.
Beyond Phosphora is a second asteroid belt.
The Planet
The world of Jazz Harmony is uniquely situated, just close enough to stay warm, and with a relatively low axial tilt—for now. It's about half the mass of Earth, but 75% of its radius and thus has a decently lower gravity. About 40% of the planet's surface is covered in water, swirling with blooms of red, black, and purple algae.
Jazz Harmony holds the unique distinction of being, not tidally locked, but in a resonance orbit of 3:2 with its home sun. Every "twenty-four hour" day on Jazz Harmony lasts for about ten Earth days; every year, about fifteen. Thus the world gains features reminiscent of tidal locking, but still follows a day-night cycle. Notably, too, there's a fairly decent eccentricity in the planet's orbit, meaning that there are "summer" and "winter" days depending on where on the planet's surface you reside.
Because of the slowness of the rotation, there is only one wind cell per hemisphere, and a single overarching set of currents within the planet's oceans. This nevertheless has created minor littoral zones, small but practical enough for life to slowly emerge on land from the planet's two large but disconnected oceans. Due to a (currently) low axial tilt of 5º, the planet also has three rough climate zones. The tropics have the longest day as well as the most extreme landscape changes; the polar regions are constantly bathed in a twilight glow, and have the most consistent icecaps; and the temperate zones are somewhat in-between, both cold and wet with a long night.
And yet it's not the worst place to live.
Picture, if you will, a typical day in the tropics. The sun rises, some six times the size of Sol in the sky, but redder and colder. A breeze blows in from the night side for some time. As the Morning draws on, the day becomes warmer, moving from tundra to taiga, then (for a few days) to rainforest. And then cometh the Storm, so big it deserves the capital letter, twenty times as powerful as the strongest hurricane on Earth sweeping across the landscape, the roaring winds matched only by the thundering of volcanoes as tidal forces sweep across the planet. At high noon–dead calm, as the Eye passes overhead, the hottest part of the day, and then back to the Storm again. And once it's passed? The glorious Afternoon, a fast-fading paradise, warm and wet and bathed in golden light. Imagine the sunset, a red world bowing out on the western horizon. Imagine (because this world has no moon) the night sky, thousands of stars burning in the empty blackness of space–silence broken only by the creaking of the week-old glaciers and the boom of earthquakes.
Imagine what it must be like to call this place home.
The Toccata-in-G-Minor Wastes, where enormous plants called overhang fronds grow in the direction of the prevailing winds and provide some much-needed shade in the tropical scrubland.
Biology
Plants
Plant life, both because of the temperature extremes and because of the high winds, generally tends to be low-lying and to have extensive root networks. Plants also, as a quirk of genetics, have five separate sexes, each of which can reproduce with any of the other four sexes but not with its own. The pentamorphic variations in structure and life cycle (occasionally quite extreme) thus can inhabit completely separate biomes and give the species a better chance of reproduction.
(NOTE: because the leaves of plants take light largely from the infrared part of the spectrum, matching Hephaestus' primary output, they look completely black to human eyes—although to Miser Crabs they spend the brighter parts of the "year" as a bright chilli, and the rest as a dark carmine.)
Multicellular plants are divided into five rough phyla:
Sporeweeds, seaweed-like plants usually found in maritime or riparian biomes. They have not yet evolved a functional vascular system, but given the buoyant effect of the water that rarely matters. Some anchor themselves to the sea- or river-bed, while others float, lily-like or in "rafts", on the water's surface. Regardless, they all share the same reproductive strategy: the release of gametes into the open sea, to swim using cilia, meet, and reproduce. Notably, sporeweed zygotes have the ability to construct a spore body around themselves until climate conditions are optimal for growth, avoiding, for example, germination during a "winter night".
Mycopoas, the earliest-found clade of terrestrial plants (although several have returned to the water). The function of a mycopora entirely depends on their thick and complex root systems. Each root puts forward several fast-growing "blades" similar to grass, until they meet another plant of the same species underground, at which point they will sprout large "mushrooms" in a matter of days—some of which reach the size of dinner plates. Those that are edible still produce hard seeds which can be ingested and excreted with minimal effort, often at some distance from the original root circuit.
Bents, the first clade of truly vascular plants. Mainly found in the temperate zones, bents are vine-like organisms which grow along the ground in the direction of the prevailing winds. Some reproduce through airborne seeds, others through pollination via patches of photosynthetic cells (originally from a single-celled "animal" infection) surrounding reservoirs of nectar. Many are simple vines, but some, like the overhang fronds pictured above, can reach truly colossal sizes. Bents are mainly found in the temperate zones.
Stiffs, the primary large plant of the tropics, and largely reminiscent of conifer trees, particularly cypresses. Notable, however, are the "stumps" that appear at various points on their trunks, concentric swirls of bioluminescent material which flicker in the long nights to attract pollinators to the ambrosia they contain (a slightly thicker version of nectar, probably closer to maple syrup in consistency).
Ixes, the fifth group, and one that has developed a unique system of parasitism. Instead of drawing on the xylem and phloem of the other plants, as parasitic plants on Earth or Ajjamah tend to do, they directly parasitize the root circuits for nutrients, minerals, and water, often becoming insanely difficult to extricate from the "host" plant. Not all these relationships are purely parasitic, however; often, with plants like the almond shroom, they provide a form of protection for the "host" through chemicals meant to discourage herbivores. Sometimes, like with the buttress-tree, they're able to provide a source of protection for plants like bents against the wind, inextricably intertwined and in full symbiosis. Ix weeds are often insanely difficult to get rid of, but they're also an excellent source of domesticable plants. They reproduce through pollination, often the same species as the plants they usurp.
Spongeworms
There are actually three completely separate lineages of animal on Jazz Harmony. The first is the spongeworms, which tend to be small organisms with very little cellular differentiation, like the corkscrew worm; conglomerate organisms like the marjaan; or simple masses of undifferentiated cells like the tissue mould, which act as the primary decomposers on Jazz Harmony. Spongeworms to a species have only one sex; they reproduce in a rather mushroom-like manner, with two individuals intertwining and a separate organism being created and budding off from their union.
Depositors
The second animal kingdom have three sexes, none of which conform precisely to "male" or "female". Like certain kinds of fish, the gametes of each species are deposited in either the open water/air or within a burrow, where they will swim, crawl, or otherwise move towards one another to form full creatures. Chromosome arrangements are thus MM, MN, or NN depending on circumstance.
The typical depositor is long and segmented, with multiple interlocked body-parts and bilateral symmetry; each segment, at least in the more primitive species, can survive if cut away from the whole, with a semi-functional digestive system, hydrostatic muscles, even eyespots. This group includes segmented animals like the winged centipede, highly manoeuverable fliers like the hummingball, shelled swimmers like the demon catshail, and even near-vertebrate forms with high flexibilty like the antlered gecko.
Dualists
The most primitive examples of this kingdom, like the colonial gliders and jellyworms, seem to be almost indistinguishable from certain species of spongeworms, but for two features. First, they cannot extrude extra tissue, being more compact and specialized in their functions. And second, they do not have one sex but two. They also tend, at least initially, towards radial rather than bilateral symmetry.
How this sex functions depends on phylum. For the jellyworms and jetfish, there are simply two types of hermaphrodite, capable of mating with individuals of either sex. For more developed creatures like the treescorpion and the crocodile steed, which have bony exoskeletons, there is almost a resemblance to Earth creatures—one individual from each sex is necessary to reproduce. For creatures with a medioskeleton, however, a partially-internalized exoskeleton creating creatures that rather resemble crustacean-like tortoises, the division is a compromise. Hermaphrodites can reproduce with one another, as well as with males, but males can only reproduce with hermaphrodites.
(A quick look at the genetic level suggests that this is in part due to the survival of the earlier depositor chromosome system. The two sex chromosomes are labeled P and Q; PP and QQ individuals are hermaphroditic, but PQ males are semi-sterile "hybrids" between the two groups.)
The Miser Crabs themselves belong to the chelonamorphs, a class with the most developed shell-like structure. (In other classes, like the cloudfish, this has been reduced to a lightweight carapace filled with air sacs to help keep creatures like the salmatross aloft.) A hint of their starfish-like ancestry is present in their ten separate "extensions" (a head, a "cloacal tail", two arms with zygodactylous digit arrangements, and six legs both for walking and for anchoring the Miser Crabs to the ground in strong winds). Most of all, however, it is preserved in their two cultural "genders"; hermaphrodites, who tend towards larger family groups and a more social setting, and males, who are generally more isolationist and prefer solitude when not strictly necessary.