(Eventually part of a larger document about the empire as a whole, but I wanted to do this part first so I could do a contest. I'd also like to note that there's not a whole lot of gender bias, the below is the norm but being trans, gendered-clothing-mix-and-match, crossdressing, and genderweird isn't exactly earth-shattering as long as it doesn't interfere with anything. I use binary terms because nonbinary people are rare enough they have to figure things out on their own rather than having a set fashion. Just putting that out there on account of being genderqueer myself; I didn't forget about us, it's just not a huge deal in this 'verse. There might be some eyebrows raised before people get used to it but so long as you don't show up to the fields in formalwear it's not going to be a problem.)

Humans: are the "lowest race" to Riraen (they're common as dirt and rarely have magic) so they're expected to cover themselves below the neck at least, and the slaves and free lower classes (anyone who isn't a craftsman) are expected to hide their heads and faces in public areas (inside a master's house it's acceptable to have the head/face showing, but not in the market). They mostly wear tough, durable clothing made of hide and leather, along with wool and linen (the latter especially in the summer time). Men wear pants and long coats of material appropriate for the season- often times their coats have hoods, but both genders might wear cloaks (fur-lined in the winter, wool or oiled leather during the rainy season). Coats typically fasten with wood or bone buttons at one shoulder- some of the lower-middle class might have iron or copper buttons.

Women laborers and farmers wear pants under short skirts while craftswomen usually wear longer skirts. Both forms of skirts have functional pockets, ranging from one or two to stick tools in to full on "I can carry ten beers" utiliskirt. Some craftswomen, such as blacksmiths and carpenters, also wear leather aprons (either half- or full), and sometimes the skirts themselves in all occupations are made of rough leather. Shirts might be loose fitting around the waist and chest, usually linen, but are tight around the sleeves, and are worn with bodices that act mostly as bras. Most women's bodices cover the breasts, but younger women (especially those who are nursing and need easy access) might wear underbust corsets instead. They aren't usually cinched in tight and aren't meant to change the shape; almost none have boning. During the winter and wetter parts of spring the shirt is changed out for a dress, often with the bodice built in. It's worn much closer to the skin (as it's usually stiffer material, either wool or hide) and laces up the back. While most of the dresses have hoods and some women wear coats like the men most also have light shawls with hoods. Light boots and shoes that cover the entire feet are the standard footwear. Riraen expect humans to wear gloves in their presence; these can range from thin linen purely for that reason to wool for winter or leather or hide for those who need to protect their hands.

A common accessory for both is a loose leather strap wrapped around the waist that hangs diagonally (essentially a lashed thong, as for a scabbard) with a loop for the main tool of their trade. There's a little bit of variation- it might have a full quiver instead of the loop for hunters, for example. 

Fabrics are usually undyed unless they work with a material that lends itself easily to dye, or they're one of the few humans of (some) status. Almost everyone stitches designs into their clothes, though. It's a point of pride, and thread is cheap. The designs usually have to do with their occupation, but scenes related to myth are common as well. 

Humans in Sezentia tend to be pale and dark-haired with light eyes in green, blue, and grey. Those who lived closer to Lita and Dasari have slightly lighter hair, but blondes are very rare.

Litan: Given that they have wings, their clothing is always open-backed (even if the wings have been removed they wear open-backed clothes to display the scars. You have to mess up really bad to become Grounded, it's for the worst kind of criminals. Before the empire the Litan used to throw them from the docks of the mountain-cities; if they survived they couldn't return and if they died then just as well. Now the Grounded are enslaved officially instead. It's not exactly a kindness.) Clothing for both genders is largely identical. Litan favor sturdy, warm clothing suitable for living in what may be the highest peaks in the world, and for flying above such. The most basic item is a leather bodysuit put together in pieces, usually a shirt and pants, which lace together into one. In winter a version with fur around the neck and wrists for extra warmth is worn.

But the Litan are also fond of colors and flowing fabric along with simplicity of design. Most, when not flying, wear an outer garment of bright fabric (traditionally spidersilk, these days they get linen and other fabrics from the rest of the empire as the Riraen dominate the spidersilk market) that can be removed and rolled easily so as to fit in a flying pack. It's something of a cross between a robe and a dress, very loose with wide sleeves and a wide, flowing bottom that touches the ground. Usually only one solid color, but some have a wide band of another color edging the neck, sleeves, and sometimes bottom. Bells are also frequently strung from the edges so they ring when they walk. The whole thing is designed to blow wildly in the wind. In the winter they wear another garment over the top, a tight sleeveless jacket that goes down to the thigh and a high collar, lined with fur on the inside.

They favor bright, vibrant colors and, in the case of two-tone garments, they don't exactly have to match. (Litan are capable of color coordination, but the garments are a celebration of color itself so it doesn't apply.)

Heavy leather bags, like messenger bags but wider and deeper, are a necessity. Most of their common tools are inside, though there are also over-the-back flying packs for journeys between cities. The side-bags are for more day-to-day activities. They latch closed with either several buttons or buckles. Litan can fit an amazing amount of stuff inside one; they're masters at packing things down to maximize space.

The Litan are delicate bird-folk with hollow bones and a natural grace. They range from absurdly short to excessively tall, with wings that (when folded) are slightly taller than they are, with each wing nearly twice as long as they are tall. They each 'mimic' a kind of bird, with that bird's wings + hair, skin, and eyes that match. For instance a pigeon Litan might be pale with a grey cast to their skin at the shadows, pigeon's wings, grey-white hair, and blue-grey eyes. They come in every bird from hawks and falcons to corvids to owls to songbirds to parrots. They're a vassal race to the Riraen, technically free (with the exception of the Grounded) but bound to a set of regulations and subservient to the empire. Both genders tend to wear their hair long and tie it back or braid it when they fly.

Riraen: are notoriously vain, as can be seen by their regulations for humans. Being blood-drinkers, they have... interesting ideas when it comes to bodies and flesh. In short: "worthy" flesh should be celebrated, and unworthy flesh should be hidden. The Riraen are, of course, worthy. The Litan are attractive enough to count as worthy, but they tend to cover themselves anyway. Dasari are usually attractive, but their blood is valuable, which means their flesh is regardless of how aesthetically pleasing they are, which makes them worthy. Humans are slower, weaker, and not consistently pretty- unworthy though they may make exceptions for those who make themselves notable. And a way of celebrating "worthy" flesh is so show it off... tastefully, of course.

Winter clothes show the least, though the cold barely affects the Riraen. Mostly they use it as an excuse to get creative with layering. Women wear a base dress in a dark color, tightly fit and floor length, with long sleeves and a high throat. The next layer is a lighter color (sometimes a lighter shade of the base color, sometimes not) with a lower collar, flowing sleeves, and either shorter or open in the front of the skirt to reveal the base color. The next layers (between two and five more depending on how extravagant they're feeling) repeat the pattern, revealing part of the skirt and sleeves below them to produce a spectrum. While the bottom is usually soft wool, the top later is almost always sheer spidersilk. In between may be particularly nice linen or wormsilk. The effect looks suitably heavy, but a human may find it insufficient and it hardly hinders the wearer at all. A type of light wormsilk cape may worn with the ends pinned over one shoulder, giving a tiered cascade to the side of waist.

Men wear sturdy pants (pants are important) and do something like the ladies' dress in reverse for their shirts. The outer layer is either a dyed leather or soft wool jacket in a dark color worn open. Immediately beneath is a soft shirt, a shade lighter, with a wide V cut exposing most of the chest. Again there are another two to five layers of lighter and thinner cloth, ending with a sheer spidersilk shirt that may or may not cover the rest of the chest or might just be a final open V. The layers are very thin and add little bulk. Men may also wear the wormsilk over-the-shoulder cape, though it's generally more opaque for them.

Most base layers (the bottom dress or the jacket) are deep jewel tones and the others lighten from there. Pants typically match the jacket in color. The only colors off limits are dark blue and dark grey, which are imperial colors, and deep red, which is the color of the Bloodrose Vanguard.

Boots made of soft leather, like lambskin, with wooden soles are worn by both. They are, surprisingly, practical and easy to move in. 

Spring and autumn wear are very similar. Women wear a dress made of light fabric (worm- or spidersilk, opaque except for possibly the ends that form the skirt which may fade to transparent) wrapped around fine but strong gold or silver chains. The chains form the skeleton of the dress, and a single, very long piece of fabric is woven over and under that skeleton starting under the chain between the breasts- the fabric is put halfway beneath that first chain as a start, and both ends wrap around the body. Eventually they are left to fall flat at the front and back, forming the ankle- or floor-length skirt with a long slit to the thigh on either side. In springtime the 'sleeves' are just a wrap out off the shoulder; in autumn they're another piece of fabric folded just once over a chain that hangs over the shoulder, creating long hanging sleeves. (Inspired pretty heavily by this image, source unknown because google just gives me hundreds of tumblrs and pintrests. If anyone knows the source please let me know. For the Riraren, the fabric weaves over/under the chain to form the dress instead of resting beneath it.) Both seasons the chains may be decorated with small strings of jewels and heavy brooch-like pins that help to hold the fabric in place.

Men wear sheer voluminous shirts with wide, undefined necklines and otherwise loose sleeves that come to tight cuffs at the wrists. The cuffs are extra layers of fabric wrapped and sewn, typically patterned with gold or silver (actual gold or silver, mind) thread. Similarly the shirt is tailored to hug the body at the waist, which is also usually more opaque (as are the ends of the sleeves). Sometimes the shirts have lace-like patterns a shade lighter than the body color. (Not actual lace, just similar patterns in the fabric.) The pants are completely opaque and similar in shape to the sleeves: they go from a slightly tight waist (to complete the silhouette) to loose, ending in tight cuffs at the ankles made of gold or silver patterned thread.

Colors are much the same as in winter (with the same restrictions) but may be lighter as well. There's no consensus; some prefer to keep to the deep jewel tones, others feel something lighter is more suitable for spring especially.

In summer modesty goes straight out the window. All the seasons hit hard in this world, summer and winter especially. Winter bothers the Riraen little, but summer bothers everyone, especially as the main of Sezentia is flat plains and scrubland with little shade. It doesn't quite reach desert temperatures, fortunately, but people aren't exactly shy about making sure they're comfortable.

Women wear loose but narrow, smoky-sheer, shiftlike dresses that cover most of the body. They may be attached to jewelry around the neckline, in thin chains like spring/autumn wear or wider bands of precious metal for cooler days. Others simply tailor it to stay in place without adornment, giving the impression they're wearing the ghost of a dress. Some use clever patterning of the fabric, jewelry, or beading to provide a little modesty but none see it as a requirement. (Think the lovely grey ladies from John Galliano's winter 2009 only more colorful.)

Men typically go shirtless, sometimes with a shorter, shirtlike version of the winter cloaks: a rectangular piece of fabric pinned at the ends over one shoulder, except this one's fold goes over the opposite shoulder, leaving the fabric to drape across the torso. They're always sheer. They wear either mostly-sheer loose pants (usually opaque at the waist and crotch fading to transparent at the ankles) or long sheer skirts with a belt/skirt of long rectangular fabric wrapped around the waist and folded in front and back to cover the crotch/backside.

The royal family has its own style, more austere and serious, no one doubts their worth so they don't have to advertise.

All seasons the shoes are soft, practical, and dyed to match. During the summer many forgo shoes altogether if they don't plan on travelling.

Riraen are pale to light skinned, attractive, with lithe muscular builds. Their hair is often dark, and their eyes come in the full range of natural colors. They like to wear their hair long and women tie it up in elaborate styles.

Dasari: are all slaves and typically wear what their masters dress them in, typically versions of Riraen styles. Their cultural fashion is showy, to combat the swampy heat of their home region. Styles consist mostly of bandeau tops for women and sarong skirts for both genders, all in bold and heavily patterned fabrics. Patterns can consist of anything from floral designs to mythical creatures. Leather or black snakeskin belts and bracelets are very common accessories. They do wear high boots outside of the city-state so as to avoid swamprot, but bare feet are common in the city and at home.

They're naturally tan but adouva are much paler (it has to do with the blood/flesh thing), and slaves outside of the Dasari homeland might not be protected from the sun and can range all the way to deep bronze. Their hair ranges from from dark to light, and many have an unnatural tint. They don't come in completely unnatural colors like the Litan do, but brown hair might be be tinted with a bit of green, or blonde hair might have a bit of blue or silver, or Lilim's pink tint to her copper. Eyes come in every conceivable shade including red, pink, orange, yellow, violet, etc.