Avatar of Pazuzu

Amorphous. The sphere can move through a space as narrow as 1 inch wide without squeezing.

Corrosive Form. A creature that touches the sphere or hits it with a melee attack while within 5 feet of it takes 12 (2d12) acid damage. Any nonmagical weapon made of metal or wood that hits the sphere corrodes. After dealing damage, the weapon takes a permanent and cumulative −1 penalty to damage rolls. If its penalty drops to −5, the weapon is destroyed.

Nonmagical ammunition made of metal or wood that hits the sphere is destroyed after dealing damage.

Legendary Resistance (2/Day). The avatar can choose to automatically succeed a failed saving throw.

The sphere can eat through 2-inch-thick, nonmagical wood or metal in 1 round.

Levitation. The sphere consistently hovers 5 feet above the ground.

Impervious. The sphere is immune to all non-magical damage.

Lash. Melee Weapon Attack: +15 to hit, reach 50 ft., one target. Hit: 24 (6d6 + 6) bludgeoning damage plus 24 (4d12) acid damage. As an action, the avatar can make three 'Lash' attacks.

Warp Mind. Pazuzu attempts to enter a player's mind to control them. The targeted player must make a Charisma saving check DC 22(17) or be mind controlled by Gak'thul. The sphere enters the player's body and is invulnerable until the character is reduced to 1/4th of its maximum hit points or until it chooses to leave the body. On a succesful saving throw, the player instead takes 3d10(1d20) psychic damage.

If all party members are controlled, they will fight themselves in a shadowy realm. If victorious, they barf out Pazuzu's essence. If defeated, they become Pazuzu's minion

Inflict Pain. Pazuzu inflicts pain directly into the target, dealing 4d10 psychic damage. The target has to make a constitution saving throw (DC:22/18) or be incapacitated until the end of their next turn.

Gaze of the Void. Pazuzu attemps to break the mind of his target. The target makes an intelligence saving throw (DC:21/17) or loses 1d4 points of intelligence.

Shadows of the Soul. After being hit by a damaging attack, Pazuzu's avatar creates an identical shadowy twin of the performer of the attack. The shadow has only 1 hitpoint, but has the same statistics and abilities as the target. It gets its turn immediately after the current turn is finished. Only one can be in existence.

Split. The sphere splits into 1d4 new versions of itself, dividing its health pool equally, and allowing each of the spheres to use the same abilities, but weakened, as stated between brackets.

The avatar of Pazuzu has three legendary actions per round. It regains spent legendary actions at the start of its turn. It can use a legendary action at the end of another creature's turn.

Inflict Pain (1 Action). Pazuzu inflicts pain directly into the target, dealing 4d10 psychic damage. The target has to make a constitution saving throw (DC:22/18) or be incapacitated until the end of their next turn.

Gaze of the Void (2 Actions). Pazuzu attemps to break the mind of his target. The target makes an intelligence saving throw (DC:18/14) or loses 1d4 points of intelligence.

Lash (1 Action). The avatar of Pazuzu makes one 'Lash' attack.