Fear Aura. Any creature hostile to Adramalech that starts its turn within 20 feet of the her must make a DC 21 Wisdom saving throw, unless she 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 Adramalech's Fear Aura for the next 24 hours.

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

Magic Weapons. Adramalech's weapon attacks are magical.

Legendary Resistance (4/Day). If Adramalech fails a saving throw, she can choose to succeed instead.

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

At will: detect magic, fireball

3/day each: hold monster, wall of fire, dispel magic

Multiattack. Adramalech makes four attacks: one with her bite, one with her claw, one with her mace, and one with her tail.

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.

Adramalech can take 4 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. She regains spent legendary actions at the start of its turn.

Move. Adramalech moves up to half her speed.

Tail Attack. Adramalech makes a tail attack.

Fireball (Costs 3 Actions). Adramalech casts Fireball.