Two Champions in one post! Or... actually perhaps not really Champions themselves. Basically, I thought: what sort of spectacular 80s cartoon space fantasy setting can you have without a magical transforming animal for a mount? So, unicorns. They could be Champions themselves, but either one could also be used as a mount for a Champion, with the other following them around with a rival Champion for their own rider (or possibly no rider). Again, I came up with this idea more out of an urge to create general OC characters for the BoCC setting, rather than for the more specific purpose you're asking for now, so, they're probably not really suitable for that. I ask forgiveness in advance for the melodramatic language.

First: Name: Prince Faethon of the Lumicorns.

Powers and Abilities: The Lumicorns are attuned to the power of sun-, moon- and star-light. Concentrating their magic through their horns and the mystical saddle that they are each given upon reaching adulthood, Lumicorns are (almost) the fastest way to travel across the stars. Forming a shield around themselves and their rider, they can spread wings of magical energy to soar through the sky or into the heavens, and can tread on the beams of light cast by the stars to accelerate to speeds greater than any crude ship. Should they somehow face a trip long enough to tax the bubble of air they carry within their shield, they can use the light of their horns to purify it to freshness again. As Prince, Faethon is even faster than most of his kind, though like all his people, he can only reach his best speeds in his four-footed form. Though he can always use his horn to form blades of energy or fire beams of blistering light, he fights better (and actually has fingers) in his two-footed form, in which he employs his sword as an expert fencer of astonishing grace. Like all his people, Faethon can sense high concentrations of evil or dark magic, feeling them as uncomfortable intrusions on his own aura of purity.

Race: The ancient race of the Lumicorns lives in a shimmering kingdom of pristine spires and vast grassy plains, Lighthallow, deep in the caverns of the crystal planet Suzokis where the refracted light through their world's stones is focused most brightly. There they dedicate themselves to achieving ultimate purity of mind, soul and body, prizing elegance, truth and clean, clear beauty. Every one of their race is raised to become flawless in their movements and precise in their calculations, for these are the skills most necessary to traveling across the stars as they do. Soon after reaching adulthood, every member of their race goes out into the universe to seek out a rider noble enough to be worth their service, pure souls unsullied by guilt, untouched by physical temptations, and eager to seek adventure and justice.

In other words: you have to have not committed any serious crime, not be addicted to anything, not have used evil magic, be a virgin, and generally be a do-gooder.

... It can take a long time to find a rider.

But, unfortunately, the only one of those requirements that can be waived is the need to be a proactive doer of good deeds, which is just a preference. The rest of the rules are built into the magic of their saddle, and if they've been broken, the lumicorn will simply not be able to use their full light powers. Fortunately, what counts as "their rider" is a little loose (an "impure" person can be pulled up behind their rider, or thrown over their back, or most anything except actually sit in their saddle), but this limits such a person to an awkward and uncomfortable journey. Lumicorns often express regret for these restrictions, particularly when they must part from a beloved rider who has decided to marry, or "marry" (lumicorn riders quickly learn that they should tell their mounts that they're going to "marry" anyone they want to have sexual relations with), but purity is the highest ideal of lumicorn culture, and to go against their laws and traditions is, for most lumicorns, unthinkable. When the time comes that a lumicorn themselves feel a desire to find a mate or have children, they return to Lighthallow to find a spouse, and almost never leave again.

As expected, Lumicorns can be pretty judgmental, though they believe themselves to be champions of truth, beauty and goodness, and most do genuinely attempt to be understanding (in a sort of patronizing way, most often). They practice purity as an intrinsic part of their magical powers, as well as an ideal, and so don't consider it to be quite as essential for other races as it is for themselves. Their society is quite formal, with traditional ceremonies for most significant events. They are strong believers in romantic ideals of loyalty and love, devoting themselves to a rider to fulfil the former and then to a spouse to fulfil the latter. Producing children is often considered only a side benefit to marriage, and their society accepts both heterosexual and homosexual couplings so long as they are monogamous and sealed with marriage before any sexual activity. Romantic or sexual relationships with other races are scandalous even to consider, however. Sexual matters are always private; Lumicorns are often actually quite naive or even oblivious to lewdness, and are easily shocked and embarrassed by such things. They have no idea why people think their traditional modes of dress are strange. They need to be able to transform between their two shapes, do you know how tricky that is with too much clothing?

Backstory/personality: Prince Faethon, eldest of two brothers born from the royal line, was always the more stern and studious of the two, often thinking of himself as most responsible, as well. Though he appreciated art academically, as a proper part of a clean and perfect world, his sense of beauty inclined more to mathematical perfection and traditional forms of proportion and precision. He studied science, history, law and statecraft, and honed his sword skills and speed to the utmost, always claiming that when he stepped out into the universe he would find a great rider who he would guide into wisdom and righteousness, with whom he would bring justice and fairness to the most corrupted pits of the galaxy. So dedicated to his training, however, he seldom spent time with his brother, who craved affection, and Faethon lingered to complete his full studies rather than leaving together with his sibling, as he had long implied a promise to do. Thus his brother left home before him, with the assurance that Faethon would "soon catch up", and met his destiny with the darkness.

Now Faethon feels responsible for what his brother has become, and has taken it as his own personal duty to defend their homeworld, and the galaxy as a whole, from the twisted hungers and nefarious plots of his sibling and his rider, all the while hoping that perhaps there is a way to undo some of the curse.

Progress in the Battle: As mentioned, Faethon would probably suit better as a companion for a Champion rather than being a Champion himself, though he could take part. He is crown prince of his homeworld, and can call on some favors, as well as the loyalty of other lumicorns who are out traveling the galaxy. Like most of the "good" Champions, he'd probably be less interested in winning than in finding out what's going on and thwarting evil along the way. He might also see the Battle as a way to meet powerful people and maybe meet a worthy rider, or to find out some secret that would help him with his brother.

I've talked about his brother a lot, so, here's his section.

Second: Name: Prince Nithikos, formerly Prince Lampos.

Powers and Abilities: Once, when he had a different name, Nithikos was a lumicorn, wielding the powers of purity and light, like his brother and the rest of their people. Now purity is no more, and the roads of light between the stars have been barred to him, but he has gained as much as lost. Now, as an umbracorn, Nithikos enjoys the powers of darkness. In four-footed or two-footed form, he can charge his magic through his horn and saddle to spread wings of dark energy and fly through air or across space, pulling a shield around himself and his rider to preserve themselves against the vacuum. He can no longer purify the air, but he can pull a fresh supply through the shadows. In fact, he can vanish into those shadows himself, moving from any darkened spot to another, so long as he has been there before or has a solid idea where it is relative to his starting point. He is not restricted in who he can carry. The journey is almost instantaneous, even from world to world or across the span of a galaxy, and he can vaguely sense conditions at his destination before arriving, saving himself and his rider from harm by suffocation, pressure and other environmental hazards. Though he can't see in the dark any better he could before his change, he can effectively extend his sense of touch into his surroundings, feeling anything that enjoys the shadows' caresses. Combined with his ability to teleport through any darkened place to another, Nithikos is a dangerous enemy in any environment that isn't fully lit. Though he is not as fast or as skilled as his brother, the umbracorn is still a very capable swordfighter in his two-footed form, and in either shape can channel through his horn to produce energy blades or lash out with whip-like tendrils of magical darkness. He has recovered some of the magical arts of the ancient umbracorns, and has basic magical skills, though he generally has to use lengthy rituals rather than simply being able to sling spells around. He most commonly uses magic to summon minions formed from or powered by shadow magic. Inverting the abilities of lumicorns, Nithikos can sense high concentrations of purity or light magic, though it inspires a desire to subvert and corrupt rather than discomfort.

Backstory/Personality: Prince Lampos was the more sensitive of the two princes of the lumicorn kingdom, the more easily and deeply moved, the more creative, the more artistic. He craved the friendship and affections of others, but although he attended many events, took part in societies dedicated to art and poetry, and became quite popular even before he reached adulthood, his position made it difficult to fully realize personal relationships with those outside the royal family. Lumicorn society is quite strictly layered, though with a keen sense of duties, obligations and respect owed both up and down the social ladder. Even within his family, rules of behavior restricted his interactions with his elders, and the only one close to his own age and station was his elder brother, Faethon. Lampos' attempts to form a closer relationship with his sibling, however, were met with platitudes, half-hearted participations and assurances that there would be time "later". The only time he did get his brother to join him on an outing, exploring old ruins for artistic inspiration, they found a secret valley in the crystal caverns of Suzokis, pooled in shadow as much as Lighthallow was radiant with light, with ancient, beautiful buildings of black stone... which the studious elder brother realized was the home of dark magic,one home to members of their own race who had long ago employed forbidden rituals to twist themselves into black reflections of their original nature: the ancient, vanished and unspoken umbracorns. Phathon swiftly dragged his brother home and forbade him to ever return, and that was the last they truly spent time together. Though surrounded by family, servants and admirers, Lampos' sense of loneliness twisted in his heart. The thought of traveling out into the wider galaxy, where he could find someone to approach on even footing, some great-hearted person to trust as his rider and see the worlds together... why, then he could be happy, surely. So, when his brother dawdled over his training and his books, despite an assurance that they would venture out together, Lampos decided to go ahead alone.

Craving experience, he did have adventures, and saw great things and terrible, enticing and repulsive; with a talent for understanding and for feeling greater than most of his people, he became wiser than he had been. With this keen sense for the hearts of others, and with a humility and dedicated patience, he found potential riders to serve, observed and evaluated them, and time and again kindly passed them over, looking for someone with whom he could truly share everything. And, eventually, he found them. In fact, he made rather too strong a connection to his rider, and they both wanted more. They wanted each other. They wanted to be free, to enjoy the world and its hidden ecstacies, together. And Lampos found himself thinking, after all he'd seen, that the kingdom he'd left behind would not be so great to return to, full of sheltered fools and restrictions as it was. Perhaps there was another way.

With his rider, he shared his secret: had had defied his brother, and returned to the ruins of the dark kingdom that was once counterpart to his own. There he had uncovered some of the secrets of the vanished umbracorns. The last of them were long gone, lost, to what Lampos now felt a lack of understanding from their light-wielding kin. There was so much the lumicorns did not understand! But he would. They would think him mad, forsaken, cursed, corrupted, but so be it! He would be all those things! He would learn from them, and then he could teach. In the darkness of a shadowed moon, stripped bare, Lampos and his rider debased themselves with rituals of deep and deviant intimacy, and the Prince was transformed. Light lost, he became the first of the umbracorn in thousands of years, and took a new name: Nithikos. As masters of shadow, he and his rider returned to his new, old kingdom, and now plot not only to sate their own hungers, but to show the kingdom of Lighthallow and its people, and all the galaxy, the secret twisted wonders that they ignore.

... Or, that's how they imagine themselves.

Nithikos's rider was a virgin as much as he was (else they couldn't have ridden him when he was a lumicorn, of course), and though they'd both seen a few things and imagined themselves as worldly, they kind of... actually weren't. They're "depraved perverts", yes, but they're depraved perverts [i]by lumicorn standards[/i]. Any sexual contact outside marriage, with a member of another race or involving any non-directly-sexual body parts besides mouth and hands would have qualified them. That "ritual" to turn a lumicorn into an umbracorn? Mostly involves awkwardly rubbing your junk on their horn. Do you know what depths of depravity they've sunk to? Occasionally involving another person in their physical relationship, and some light bdsm activity. The "nefarious plots" they "unleash" on Lighthallow are mostly just vaguely sexual pranks, like sending shadow minions to steal clothes, it's just the lumicorns themselves who react like that's cackling villainy.

Nithikos is a huge nerd. A huge arty nerd who's kinda charming and who likes sex, but a huge nerd, still. He thinks acting like some saucy incubus is just what he's supposed to do now. Thumbing his nose at his old culture's standards gives him a little thrill, but he'd never really do anything truly harmful to anyone who didn't deserve it. When he sees people in trouble, he tries to help, though he covers it by acting like it's some clever prelude to corrupting and recruiting them to the service of darkness.

He's a pretty good guy, really.

Progress in the Battle: Right, so, as I'm sure you noticed, I talked about Nithikos' rider in totally vague terms. Aside from the fact that they were also relatively innocent/naive, and were a good enough person that Nithikos' really liked them and they were able to ride him as a lumicorn for a while, there's nothing set about them. Perhaps someone else will come up with someone who would fit in that position! I personally imagine some sort of "dark princess" character, who could counter a classic good princess character for Faethon, but there's plenty of room to be creative. Or, if you wanted to make Nithikos' story a little sadder, maybe he lost his rider somehow, and now he's alone. His involvement in the Battle of Cosmic Champions depends on what you decide. Again, like his brother, he's not really designed to be a Champion himself, but he could be. Since he's a cursed betrayer of his people's ways, he doesn't have access to the resources his brother has, but he can return to the ruined kingdom of the umbracorns as easily as traveling to any other dark place, and it actually has a variety of ancient magical comforts that still work and that he's learned to operate, somewhat. He has small, effectively harmless shadow minions who grow food in the black gardens and do chores for him, and he can summon them from shadows wherever he is, though they evaporate in bright light. He can make a few more powerful minions (think animated black rose bushes, or golems of smooth, rounded dark stone), but they take time and effort and aren't that much less fragile.

tl;dr summary:

In a magical crystal kingdom inhabited by beautiful slender unicorns, who can transform into beautiful slender unicorn people and who are all basically paladins with magical light powers, there were two princes. They went out into space on a journey to find worthy riders they could serve as mounts to, but one of them discovered he liked sex and decided he'd give up the silly purity thing, and swapped his light powers for dark powers and embraced an ancient legacy of being a hedonistic seductor sorcerer supreme, but he actually has only a rudimentary idea of what that's supposed to entail. Now the two brothers are locked in an epic struggle between good and evil, only replace "good" with "prudish but well-intentioned ideas of romantic purity and chivalry" and replace "evil" with "earnestly attempted but awkwardly ill-understood ideas of romanticized hedonism".