Archfiend of Infnir

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

Multiattack. The archfiend makes two attacks with its claws, one attack with its tail, and casts one of its "at will" spells. Alternatively, it can make two Spectral Blade attacks.

Claw. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit: 15 (2d8 + 6) slashing damage + 6 (1d12) necrotic damage.

Tail. Melee Weapon Attack: +12 to hit, reach 15 ft., one target. Hit: 12 (1d12 + 6) bludgeoning damage.

Spectral Blade. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit: 13 (2d6 + 6) slashing damage + 19 (3d12) necrotic damage.

Teleport. The archfiend magically teleports, along with any equipment it is wearing or carrying, up to 200 feet to an unoccupied space it can see.

Corrupting Presence. Each creature of the archfiend’s choice that is within 95 feet of the archfiend and aware of it must succeed on a DC 19 Wisdom saving throw or become frightened for 1 minute. While frightened in this way, the creature is poisoned and takes 1 necrotic damage at the start of each of its turns. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature’s saving throw is successful or the effect ends for it, the creature is immune to the dragon’s Frightful Presence for the next 24 hours.

Innate Spellcasting. The archfiend’s spellcasting ability is Charisma (spell save DC 22, +14 to hit with spell attacks). The archfiend can innately cast the following spells, requiring no material components:

At will: detect evil and good, detect magic, bestow curse, ray of enfeeblement, animate dead, fireball, suggestion

2/day each: raise dead, scrying, circle of death, soul cage, forbiddance, mass suggestion

5/day: power word stun, teleport, true seeing, gaseous form

The archfiend 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. The archfiend regains spent legendary actions at the start of its turn.

Detect. The archfiend makes a Wisdom (Perception) check.

Bite. Melee Weapon Attack: +12 to hit, reach 5 ft., one target. Hit: 9 (1d6 + 6) piercing damage + 4 (1d8) poison damage + 3 (1d6) necrotic damage and the target must succeed on a DC 16 Constitution saving throw or have its hit point maximum decreased by the amount of necrotic damage dealt. This reduction lasts until cured by a lesser restoration spell or similar magical effect.

Wing Attack (Costs 2 Actions). The archfiend beats its wings. Each creature within 10 feet of the archfiend must succeed on a DC 21 Dexterity saving throw or take 12 (1d12 + 6) bludgeoning damage and be knocked prone. The archfiend can then fly up to half its flying speed.