Seelkadoom appeared in sonic RPG 1 he was created by Dr eggman using the two most powerfull hedgehog and chaos energy. All tho seelkadoom never obey eggman his own master and go on his way trying to destroy his two brother. Then again he meet a evil friend call reala but then reala meet up with his enemy nights and shadow and go destroyed now the epic battle begin in sonic RPG 8 when sonic and shadow go up against the evil brother seelkadoom but tonically sonic got beaten leaving the only one standing all tho nights and knuckles came in sonic RPG to help shadow stop seelkadoom they got knock out leaving shadow again then shadow go up against brother by him self but lost against him . then something great happened. From the way I see it sonic refused to lost to his evil brother. He got back up and turn super sonic but that’s not all. He draw’s energy from shadow chaos emerald known as the sapphire emerald and used it to go hyper sonic then the real showdown begin. I don’t really know about sonic RPG 10 because it never came out