Rainbow's Heaven Sword (虹天剣 Kōtenken ) is Merihim's signature Unrestricted Spell. It fires a destructive ray of rainbow. While charging the spell, a halo-like rainbow light glows on Merihim's back, resembling wings. This spell is counted as one of the greatest offensive powers of all time. He also has the mirror-shaped Rinne army called Aeria, which acts as the reflector for his fired Rainbow's Heaven Sword to his enemies when they had evaded the first attack but would instead fall under his "next" attack or the reflected Rainbow's Heaven Sword. He is able to use the "Rainbow's Heaven Sword" to defeat Orgon in one strike.