Artwork credited to Timmiboi.
Adagio was in an accident when he was still young (Classified and redacted) and deemed legally dead by the military, and used as test for a new super-soldier program by the military, but his, left ear and eye and his right arm was beyond help, and was replaced by bionics.

But what the military didn't know was that the experiment would cause an unintended side effect, IE: drastically extended lifespan, scientists were baffled and eventually gave up. but one of them knew the answer, and later came to be Even's (Now code named Adagio15, because of his slow cellular degeneration, * Adagio: (especially as a direction) in slow tempo. *) only friend...

His slow aging at first was a blessing, (He could see the world change due to his genetics, a world of humans, is now a world of anthropomorphized animals) soon became a curse, and after seeing his second child die of old age, he decided to, as he put it; Put an end to the abomination the world has become...