Ideal Masters

Rulers of the Soul Cairn, they resemble glowing crystals that seem imortal like daedric princes. They tricked Durnehviir into guarding the Soul Cairn for eternity and seem to enjoy making deals with necromancers. In The Elder Scrolls V: Dawnguard they possibly appear as large, floating soul gems that drain the dovakiin's health as he gets near and cannot be harmed in any way.