Complex sentence: Soatome is an assassin, skilled in various forms of black magic, who works in the same department as Sabrina, however, he also wishes to be the leader of the underground society that seeks out Boy.
Split into simpler sentences: Soatome is an assassin, skilled in various forms of black magic, who works in the same department as Sabrina. However, he also wishes to be the leader of the underground society that seeks out Boy.