How did this all begin?
Kater could never remember. All he remembers is beginning a team of admins and lackeys, wanting revenge for some arbitrary feeling. Maybe it was loss, and a childish tantrum of a reaction? Was it out of spite of some expectations forced upon him? Did he snap and break mentally and stayed insane until that fateful day? Did he have such a world-changing idea rejected, to the point of gathering people who agree with him to create an almost cultist group? Did he desire attention, and made false claims to gather people to worship the very ground he walked on? It was all such a blur. There was only one clear memory of those dark times, one shining memory among those blocked out for what was most likely for the better.
The boy.
His name was Victor, as far as he could recall, a boy that was only supposed to be a short problem, to be quickly resolved. But as time passed, he learned of him slowly defeating his admins, making his way to him. It was a stormy day when the boy got to him, and Kater found himself standing there, in the rain, before a boy blessed with strength and luck. And the boy was angry. Apparently his admins caused the death of his best friend. He didn't blame him for such rage, but Kater himself was at the point of no return, was he not? He had blood on his hands now. And the boy wanted a fight, revenge for the fallen. Who was he to say no? He did not falter during the fight, though. Victor wanted his fight. He had a fire in his eyes. He deserved at least his all.
His all wasn't enough.
He can remember hearing thunder crack and rain pour as he fell to the floor, Victor seeming to leave, only to come back and to yell at him. He was practically venting to him, a villain of all things. Despite the ringing from the attacks, the storm brewing even move above their heads, he heard it all, loud and clear. "Leave this place forever." was the last thing uttered by him, before holding out his hand for his pokemon. Kater picked himself up slowly, waddling out. His team, his beloved team, was left in the hands of this trainer, a soon to be champion. He gathered his stuff, being watched over by the boy to make sure he didn't do anything to keep control of his team. But he didn't care at that point. He knew that he had done wrong, even if the years of evil schemes were lost to his brain, most likely realizing his mistakes before the battle had even begun. After that, he disappeared from the mainland with only an egg and a suitcase, exiling himself to an island miles off the coast. A voluntary decision, but he most likely would've gone there anyways. Kater still remembered the people hiding or yelling at the fallen leader. It was clear he wasn't wanted there anymore. He was gone just like that, out of sight and out of mind.
And now he was isolated from society, with only a house on a barren island and a Goomy to keep him company.