Destioss is half of a soul, the other belonging to Positoss, meaning Destioss can't be properly killed without Positoss dying with him.
Before being forced to convert to his new evil personality and form, Destioss was better known as Destiak and one of the greatest warriors of his time. He was originally going to share the "Oss" position alongside Positoss. Although this did happen it didn't go to plan.
Destioss was the first to be put under Shadow's influence, giving him the fitting status as their leader. Destioss like his possessor, had his physical form altered by Shadow's power, along with his brain, giving him much of Shadow's personality while keeping some of his own.
Shadow corrupted Destiak on his way to a friend of his informing him of his plan on a new system of leadership. Destiak's physical form was distorted and warped, gaining red eyes and being a dull olive colour instead of gold. He then killed him before he could send Destiak to the current Oss with this new leadership system.
Destioss is the leader of an empire he created by "passing on" tiny fragments of his atomized possessor (like a plague or disease), mutating them too.
Destioss before his corruption appeared just as a normal member of his species would, however with three spikes on his helmet/mask and thick shoulder plating, standing at 7.5 feet tall.
After the corruption he grew to 8 feet in height, developed blade-like teeth and red cat-like eyes, he is notably taller than his previous form with some parts of his armor being altered too, making it look spikier or enlarged in some spots. his hands are also deformed, a shortened palm with extended fingers, similar to daggers.
Before his corruption, Destioss had decent personality which was destroyed in his final mutation stages.
Today, Destioss doesn't know the emotion of happiness and believes death isn't a cruel enough punishment. He is angered by emotional situations and has never known fear.
Destioss makes up for his negativity with his intelligence and his ability to remain calm in any situation.