Eh, my hero power is basically already a villain power. "Demon" Lord: Turn people into your vassal/familiars. When a familiar dies, you or another familiar may resummon them at a small mana cost. There's more, but that's the most important bit- It's an unkillable demonic invasion.
Theme = Secrecy Signature = a dead starved/dehydrated business owner Power = creation and management of pocket realms/dimensions
Theme: Chaos Signature: A giant flying bull with gentle eyes Superpower: shapeshifting, reality alteration, controlling the realms of madness, and pie.