Rias is a high leveled necromancer, he is the cause of why the world is in ruins right now. Plenty are unknown about him apart from the fact that he's a massive threat. Way too many people had tried to kill him but to no avail. He might be quiet but there are instances that show off his lack of sanity. Often shakes as if he's dying, it's a wonder how he can still be alive. A man of sorrow, his former ambition gone. Kill, revive and repeat is his every day routine on his mentor.