Demon Lord's Haki

Demon Lord's Haki (魔王覇気) is an Extra Skill only obtainable by magical beings who have reached the level of a Demon Lord. It is also an Intrinsic Skill of Demon Slime, though Rimuru is the only one to have ever existed in history.

Abilities
It combines the effects of the Extra Skill Haki and Magic Aura and allows the user's aura to exert a powerful spiritual pressure over their targets and inflict them with potentially lethal magical effects. It is possible for one to immediately perish if they are too weak, or cause one to lose their sanity.