Cusps
When it comes to reproduction, not all zodiacs can breed with each other. One might think these lines are drawn based on anatomical lines. Like, surely the sheep and goats can make babies, right? And crabs and scorpions are relatively similar compared to other zodiacs - them too, right?
No. You fool. The sheep fuck fish and the crabs bone lions.
The lines, instead, are drawn based on the order of the zodiac, the ability to make hybrids symbolizing the astrological aspect of "cusps"; those born on the borderline between sign dates. This means that Geminis, for instance, can reproduce with Taureans and Cancerians, but not Sagittarians. Ophiuchi and Cetans, not being real signs in terms of the Actual zodiac, are only capable of reproducing with each other. Araneans are in a similar boat, but work... quite differently. We'll get into those.
Not all hybrid pregnancies result in cusps, especially if a parent was a cusp themselves, but the majority do. It's thought that prayer can swing things one way or another, or that conceiving during a cusp date will up the odds of the baby being a hybrid. It seems these tactics work well despite the lack of biological sense, but that's rather commonplace for Siderea.
Cusps can vary even with in their own "species", sometimes taking after one parent more than the other and thus having one zodiac more predominant in their features. Overall, though, they tend to be easily identified as a hybrid. They are common enough that they each get their own name - much simpler than having to say Virgo-Libra hybrid or whatever every time! The cusps are as follows:
Aries + Taurus = Aurus
Auruses typically have the build of Tauruses - tall, generally large one way or another - but the fluff of Ariens. Their tail is like a Taurean tail, but with floof instead of just hair at the end. Their horns can go either way but are typically a combo of both, being large and broadly curved. They're renowned for their might and considered to be the strongest species in Siderea, physically speaking.
Taurus + Gemini = Taumini
Taumini also are primarily based off of Tauruses, albeit now with a pollux. The pollux always encompasses at least their legs and horns, with their tail being replaced by a Gemini-styled tail. They tend to be shorter than normal Tauruses and may have Gemini ears (pointed ears) instead of Taurean ones. Offworlders often mistake them for demons.
Gemini + Cancer = Gemcer
Gemcers take after Cancers, but their shells are all replaced with a pollux instead - albeit a sturdier, more fragmented one than the norm. It's weaker than a normal Cancerian shell, but makes up for it in being flexible and customizable. They're amphibious and lay eggs like Cancers, but tend to have the ears and tails of a Gemini. Because their shells are made of their pollux, they don't shed like Cancers. Rarely a Gemcer will instead have their pollux attached to their skin rather than comprising their shells and may struggle to maintain a shell over life due to the difficulties in shell regrowth after shedding.
Cancer + Leo = Canceo
Canceos have a lot of variability in which half they take after most; some are mammalian, some are crab:tm:, some have shell ears, some have cat ears, some have both, it varies quite a bit! What's consistent is that they always have some amount of carapace, plenty of fur, and a Leonine tail. Most are amphibious, but rarely one that take heavily after their Leonine parent won't be.
Leo + Virgo = Lirgo
Lirgos also vary highly, with some being more plant-like and others being more mammalian. Whatever the case, they mix flora and fauna, often having layers of fur between layers of petals and leaves. Their ears and tails tend to be furry/bushy and not quite Leonine, often more wolf/fox-like. Erune granbluefantasies but like also salad.
Virgo + Libra = Vibra
Vibras tend to resemble living statues overgrown with flora, but don't struggle with movement or weathering as their appearance might suggest. Some are more "plasticky" or porcelain-like (as Libras are), but it's common for them to seem made out of various kinds of stones or gems. They can't "customize" themselves quite as easily as Libras right out of the box (womb...?) and their chrysalises (covered in vines rather than filigrees) require some maintenance if they go that route (functioning something like a seed, doing best when buried and watered), but in general they follow the same "rules" as Libras. They tend to be exceptionally long-lived, but are one of the rarest cusps.
Libra + Scorpio = Librio
Librios take most after Libras, but rather than fancy metallic filigrees, Librios have carapace in various places. They also have a Scorpion tail, though by default their poisons are less potent than a normal Scorpio's. They may have Libran "horns", Scorpion "chelicerae", or both. Instead of Libran "wings", Librios have appendages on their back that vary from Librio to Librio but resemble parts of other insects. These manifest as insectoid wings (sometimes with an associated shell like with beetles), praying mantis forelegs, or generic insect legs. Librios have an easier changing themselves up than Vibras, and their chrysalises - which often look like Actual insect chrysalises - while more fragile, require less maintenance.
Scorpio + Sagittarius = Scarius
Scarians are known for being a bit, well, scary. They're scorpion taurs, having the top half of a Sagittarius (in other word, a human with horse ears, though they often have the "chelicerae" of a Scorpio as well) and the bottom half of a scorpion. They can shift into a satyr form like Sagittarians, gaining the legs of a Scorpio and either keeping their stinger or having it replaced with a horse tail depending on the person. While their poison also isn't as potent as a normal Scorpio's, their larger size means it's easier for them to inject/dispense more poison at once, making them a great help in the business of scorpion wine!
Sagittarius + Capricorn = Sagricorn
Sagricorns use Sagittarians as their base but are clearly quite different. For starters they have a single horn hailing from their Capricorn heritage, making them unicorns. Their horse coats are incredibly fine and silky, either being extremely short and speckled with scales or extra long so as to resemble the ocean waves. Their hooves and horns are typically iridescent and highly valued on the black market. In water they can transform their back halves into a tail just like Capricorns. Like their parents, Sagricorns can adopt a satyr form, where whether they have a horse tail or fish tail depends on the person.
Capricorn + Aquarius = Capriquarius
Capriquarians tend to have long hair, drooping ears, and large horns that curl downward. Their satyr form is a good base to start with, as a Capriquarian's legs are basically just. water. They're more like glass filled with water, sometimes speckled with scales. They don't struggle with moving and they seem just as sturdy as normal legs, however, so it's just #aesthetic. In actual water they vanish, being replaced by just a fish tail. This leaves them more resembling a Pisces, albeit with goat ears/horns/eyes.
Aquarius + Pisces = Aquisces
Aquisceans resemble Pisceans, what with the whole mermaid thing, except the mermaid tail is made out of water & air. They tend to have cloud-like hair, and rather than fin ears they have wing-like ears. They can float in the air just as easily as they can swim underwater and thus have less need for a two-legged form, but they can still shift into one. In this form their legs tend to be airy and cloudy as well, not really resembling human legs much. Their Piscean cords may be found further up on the spine like wings, but otherwise function the same and permit them access to the Dream Sea.
Pisces + Aries = Piries
Piries split their parentage fairly evenly, having both an Arien form and Piscean form. In either form they have ram horns, ears, and eyes. In Piscean form they have a fish tail, though it's usually ringed by fluff. In Arien form they have their fish tail in place of a ram one, but otherwise don't look much different from a normal Aries. Fish tail kinda noticeable though. Their horns and hooves tend to be more colorful than those of standard Ariens, but this isn't a rule. Likewise, they may have scales scattered elsewhere across their body in either form, but not necessarily. Piriens almost always lack cords, meaning they cannot access the Dream Sea like a normal Pisces. However, lucid dreaming comes naturally to them and they may end up wandering about the Dream Sea and even getting involved in dreamwork; they simply lack the connection between dreamself and wakeself and lose their Dream Sea presence upon awakening. Very rarely a Piries may be born with functioning cords, and such a thing is considered a great blessing and sign of power.
Ophiuchus + Cetus = Ophietus
Ophietuses are very sea snake, perhaps skewing eel, essentially being Ophiuchi with aquatic, abyssal theming. They may or may not keep their halos and wing ears, the latter being swapped out for standard Cetan ears instead sometimes. Likewise, they may or may not end up with the black sclera and immense size of Cetans. The matter of size is incredibly unpredictable and inconsistent: unless born to the Cetus in the relationship (and often even then), typically an Ophietus will be born and grow up at normal Ophiuchus size. Once they reach maturity, they either stop growing, start growing rapidly until they reach full Cetus mode, or simply never stop growing and reach Cetus size over a long period of time. Because of the hassle this presents, Ophietuses will engage in all manner of diets, remedies, and spells to either prevent, stunt, or promote growth depending on which side of society they'd prefer to stay on. An Ophietus can become even larger than a pure Cetus thanks to their tails: Saint Leviathan, for instance, is the largest living being who's ever existed on Siderea. Given the history of Cetans, it should be no surprise that this is the rarest cusp.
Arachne + ...?
Araneans are... complicated. Outside of each other - and that's not something that's been experimented with much considering the species has only been around for a few decades, if even - Araneans reproduce by conversion. Long story short, they take other species and turn them into Araneans, making all of them other than Arachne herself "cusps" in that they have traits of both species. While from the waist-down they'll be spidery, their top halves remain unchanged. Repeated conversions can change this, adding traits like additional eyes and chelicerae, but overall it's easy to tell what species an Arachne once was. Their spider halves may even have traits from their former species, like Arien Araneans being fluffy and Cancerian Araneans having armored legs. While all Araneans are recognized as Araneans first and foremost, where it's relevant a unique name may be used to indicate what they're a hybrid of, with the current list being the most popular but not unanimous terms:
- Aries: Arachnaries
- Taurus: Taurachne
- Gemini: Arachmini
- Cancer: Arachcer
- Leo: Leorachne
- Virgo: Virgachne
- Libra: Librachne
- Scorpio: Scorachne
- Sagittarius: Arachtarius
- Capricorn: Arachorn
- Aquarius: Aquachne
- Pisces: Arachsces
- Ophiuchus: Ophiuchne
- Cetus: Arachtus
Cusps are only capable of breeding amongst each other and their component parts, often leading to their child being the same hybrid as them but limiting the potential of wild chimeras. With the power of magic it's not completely impossible for other hybrids to exist, but any such individual would be a one-off kinda deal rather than something that happens with any sort of regularity.
Due to being inherently rarer, Siderean society tends to view them as somewhat special. It's nothing overbearing, though, and the sort of thing that's become less and less common as society progresses and cusps become more common. Though it's something of a contradiction, despite this admiration non-cusps are very much considered the "default" in a sense that offworlders are often surprised when they visit and find that, by their culture's terms, the listed number of Siderean races really ought to be doubled!