Power Aura. Any creature hostile that starts its turn within 20 feet of Alistair must make a DC 18 Wisdom saving throw, unless Alistair 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 Alistair Power Aura for the next 24 hours.
Magic Resistance. The pit fiend has advantage on saving throws against spells and other magical effects.
Magic Weapons. The pit fiend's weapon attacks are magical.
Innate Spellcasting. The pit fiend's spellcasting ability is Charisma (spell save DC 18). The pit fiend can innately cast the following spells, requiring no material components:
At will: detect magic, burning hands
1/day each: thunder step
Multiattack. Alistair makes three attacks: one with its bite, two with its claw,
Bite. Melee Weapon Attack: +1 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 8) piercing damage. The target must succeed on a DC 18 Constitution saving throw or become poisoned. While poisoned in this way, the target can't regain hit points, and it takes 12 (2d6) 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: +10 to hit, reach 10 ft., one target. Hit: 17 (2d8 + 8) slashing damage and 6 (2d6) fire damage
Fight it . Try to fight the power of Gargauth, push him out of your brain and your soul, make a DC 18 Wisdom saving throw, on a sucess you take 5 (1d10) psychic damage and help to lower the influence of Gargauth, on a failure you take 10 (2d10) psychic damage
Embrase it . You embrase the power of Gargauth make you and him one and heal yourself of 5 (2d6)
Alistair can take 3 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. Alistair regains spent legendary actions at the start of his turn.
Immolating Flame (Costs 2 Actions). Alistair turns his magical flame toward one creature he can see within 60 feet of him and commands it to combust. The target must succeed on a DC 18 Wisdom saving throw or take 12 (4d6) fire damage.
Claw. Alistair uses his Claw action.
Alistair Battle Memory. Alistair remember is true self for a strategic replacement and can move up to 30 feet away from a enemy.