he wants to know who the emperor is in this game, not some fan fic about himself.
It's not a fan fic, its a dossier on the Emperor. And no, he was not Abeloth (who was female). But Tenebrae, the illegitimate son of Lord Dramath of Medriaas who took the title soon before the Great Hyperspace War and after that took the survivors of the war to Dromund Kaas. The reason he is so powerful is because he performed a ritual on his home planet of Medriaas (which became Nathema - being from anathema meaning cursed) which killed everything on the planet and made him 'immortal'.