Brain of Cthulhu

Creepers. The Brain of Cthulhu has 30 Creepers, and is immune to all damage while at least one of the creepers are alive. The Brain regains all creepers at dawn each day.

Cranial Maw. If the Brain of Cthulhu has no creepers left, it turns into it's 2nd form, gaining 10 ft of flying speed and its slam attack deals an extra 10(3d6) damage.

Ghosting. The Brain can pass through all solid surfaces including walls and the ground without disturbing the material it passes through.

Create Duplicates(2nd form only). The Brain of Cthulhu makes 3 duplicates of itself that last for 1 minute. A creature can make a DC 10 INT(investigation) check or a DC 10 WIS(perception) check to determine the right one. the DC goes up by 2 when the Brain has less than 70 hit points, goes up another 2 if at less than 45 hit points, and goes up by yet another 2 at 20 hit points. If a creature hits a duplicate, the attack does no damage to the Brain. the duplicates themselves deal no damage and the Brain cannot make more duplicates until the current duplicates fade.

Slam. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit:  13(2d10 + 2) bludgeoning damage.