Black Avatar of Tharizdun

Legendary Resistance (3/day) If the Black Avatar of Tharizdun fails a saving throw, it can choose to succeed instead.

Teleport Without Error. If attacked, the Black Avatar of Tharizdun will teleport away as long as it is able. It can do this at any time.

Dark Aura. Once, daily, Black Avatar of Tharizdun can create a wall of darkness as a bonus action. This does 9 (3d6) necrotic damage to any creature within 10 feet of it, besides Black Avatar of Tharizdun and creates magical darkness around it, as if casting the darkness spell within that 10 feet.

Touch of Madness. If Black Avatar of Tharizdun hits with melee weapon attack, the creature hit must make a Wisdom Saving Throw or suffer short term madness determined by the GM (DMG p. 259). Additional melee weapon hits from Black Avatar of Tharizdun cause the Madness to increase to Long Term, and then Indefinite Madness.

Multiattack: The Black Avatar of Tharizdun makes two attacks. One with it's Javelin and one with its Antlers.

Antlers. Natural Weapon Attack: +5 to hit, reach 5 ft., 1 target. Hit: 10 (1d10 + 5) bludgeoning damage. 

Javelin. Melee Weapon Attack: +10 to hit, range 5 ft., 1 target. Hit: 16 (3d8 + 8) piercing damage.

Legendary Actions. Black Avatar of Tharizdun can take 3 Legendary Actions, daily, choosing from the options below. Only one Legendary Action can be used at a time and only at the end of another creature's turn. For spells, Black Avatar of Tharizdun's spellcasting attribute is Charisma.

Tharizdun's Will. Black Avatar of Tharizdun casts Circle of Death.

Tharizdun's Curse. Black Avatar of Tharizdun casts Disintegrate.

Tharizdun's Voice. Black Avatar of Tharizdun casts Dominate Person.