Fear Aura. Any creature hostile to Xurgorok that starts its turn within 20 feet of him must make a DC 21 Wisdom saving throw, unless the pit fiend is incapacitated. On a failed save, the creature is frightened until the start of its next turn. If a creature's saving throw is successful, the creature is immune to the Xurgorok's Fear Aura for the next 24 hours.

Lesser Fiery Regeneration. When Xurgorok takes fire damage, he instead heals half the damage taken.

Magic Resistance. Xurgorok has advantage on saving throws against spells and other magical effects.

Magic Weapons. The Xurgorok's weapon attacks are magical.

Innate Spellcasting. Xurgorok's spellcasting ability is Charisma (spell save DC 21). Xurgorok can innately cast the following spells, requiring no material components:

At will: detect magic, fireball, Eldritch blast (17th Level)

1/day each: mental prison, forcecage, maddening darkness

3/day each: hold monster, wall of fire, dominate person

Multiattack. Xurgorok makes four attacks: one with its bite, one with its claw, one with its mace, and one with its tail. Xurgorok can forgo his bite attack and hit twice with his mace.

Bite. Melee Weapon Attack: +14 to hit, reach 5 ft., one target. Hit: 22 (4d6 + 8) piercing damage. The target must succeed on a DC 21 Constitution saving throw or become poisoned. While poisoned in this way, the target can't regain hit points, and it takes 21 (6d6) poison damage at the start of each of its turns. The poisoned target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Claw. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 17 (2d8 + 8) slashing damage.

Mace. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 15 (2d6 + 8) bludgeoning damage plus 21 (6d6) fire damage.

Tail. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 24 (3d10 + 8) bludgeoning damage.

Blessing of Hidoi. Xurgorok can use a bonus action to silence the flames of his mace and coat it with his master's cursed saliva. The target must succeed on a DC 21 Constitution saving throw or be cursed with Necrosis as blood cease's flowing efficiently throughout the body. The cursed target can't regain hit points, and its hit point maximum decreases by 12 for every 24 hours that elapse. If the curse reduces the target's hit point maximum to 0, the target dies, and its body turns to into a dried up pile of flesh. While cursed in this way, the target can't regain hit points. The curse lasts until removed by the remove curse spell or other similar magic.