Subject Name: Sombor Viraxis
Species: Human
Species Mutation: Minor Technopath
Xeno-Ancestral Awakening: Osmosian
Reality of Origin: Currently unknown
Viraxis, like all Osmosians, is the descendant of extinct race of beings from the Andromeda Galaxy known as Vicendians. At some point, their home planet, Osmos V, was swept up in a cosmic storm, a cast-off of the birth of a To'kustar.
Many species who had undergone similar disasters had either perished, or the Species had undergone a mutated Awakening of some minor ability. Aerophibians gained the ability to slip into hyperspace, Vaxasaurians went from skin thickening to sextupling in size. The ancestors of modern humanity gained a potential for variable mutation. In the case of Vicendians, a minor ability to absorb electrical energy evolved into the ability to absorb and become matter, and, as they would discover, DNA itself.
Such gifts came at a cost, however; the Vicendians' fertility with each other become nigh non-existent without the Absorption of DNA. They were the only sapient race on their planet, with the instincts from animals quickly wreaking havoc on their sanity. To save their dying race, they would spread throughout their galaxy, and use wormholes to travel to others, absorbing and mating with countless other species. Time passed, and the original Vicendians eventually went extinct, with only legends, the Osmosians themselves, and a genetic compatibility between vastly different species as evidence of their existence.
Sombor Viraxis lost everything he cared about at a young age, and was determined never to lose anything again. He would be inspired by the tales of Ben Ten's battles, but not by Ben himself. The stories of Aggregor, Vilgax, Dagon, and fellow Human Osmosian Kevin would inspire him to take power in a way that could not be taken back.
Years later, with the gathering of allies who suffered similar tragedies, he would capture Ben 10,000. With technology based on the power absorption methods created by Aggregor and Psyphon, he would created clones of the various transformations. Turning them into pure energy, and using the Potis Altiare as a filter to enhance the resulting powers and reduce weaknesses, he would gain the abilities of countless alien species, able to call upon or store them at will.
With technology based upon the Ultimatrix, his body was evolved to handle the entirety of the powers bestowed on him, with no impact to his sanity. This would also make it impossible to take away the powers through absorption, as well as allow him to mutate others into hybrids at will.
Even with the precautions to make absorbing them out of him impossible, Kevin Levin and Gwendolyn Tennyson still stopped him before he could create a clone of the sole fusion he sought, Atomic X. With phenomenal cosmic power out of his grasp, he and his allies now use his Chronosapien abilities to travel the multiverse, repeating their plan upon countless versions of Ben Tennyson or other Omnitrix wielders to gain more species' powers. But no reality he has visited thus far had held the Biomnitrix, nor even the Ultimatrix.
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This is mostly an excuse to show a headcanon I made on how to mold together the different Canons on Osmosians in UA and OV, since Servantis's explanation ignores both Aggregor and Ragnarok, and the idea that they were both Rooters is kinda dumb.
So, there was an original DNA-absorbing species, but they are long gone, and Osmosians are their descendants who awakened their power. Azmuth is old enough to remember them, and Paradox is a Time Lord. Thus, Servantis, who knew nothing of this extinct race, made up the term Osmosian - not knowing that Osmos V was the name of an actual planet. Devin did exist, but was just considered a mutant, since Osmosians were rare as heck in the Milky Way.
Aggregor's family line (he is not human) managed to keep the power and stories of Osmos V intact throughout the millennia, hence why he knew where the planet was.
I also added in connections to some other phenomenon in the series.
So, the same cosmic storms that create To'kustars also cause the more out-there or physics-defying abilities some aliens have, especially the ones that make you go "Why did they evolve that?" Them affecting ancestral human DNA to cause modern-day mutants is based on the Marvel Comics canon of where the X-Gene comes from.
Hell, considering To'kustars can create cosmic storms, you could even have a less compassionate one throwing them at planets on purpose to experiment.
As for Sombor, this is just me going, "How powerful could an Osmosian get without a Celestialsapien?" I should note that he avoids permanent absorption of Ultimate Aliens - he is actually very careful to not go nuts, and the Ultimates are instinctively driven to combat and conflict. Something he wants to avoid. Temporary absorptions at best. And Anodites? He can't keep any of them down long enough for a permanent boost.
This is also why he wants Atomic X, and not Alien X - just like Aggregor, he doesn't want to get soft-locked.
The last name Viraxis, comes from the Latin words Vir and Actus, meaning Man and Action. (Man of Action)