The Illusion Elemental is the fourth secret boss in Circle of Blood. He can be found behind the one statue lit with blue-green flames. The prize is the Aqua Key.
The Elemental will quickly teleport around the room. He can duplicate himself, so the duplicates must be killed quickly. He can summon energy beams from the ground, toss cursed spheres, raise poisonous plants, and summon flames from the ground. Later, he can shoot an arrow which will paralyze, and he can explode, dealing random status ailments. He has 6000 HP, and his theme is the Judgement version of Elemental Tactician.