Asmodeus

Legendary Resistance (3/Day). If Asmodeus fails a saving throw, it can choose to succeed instead.

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

Reflective Carapace. Any time Asmodeus is targeted by a magic missile spell, a line spell, or a spell that requires a ranged attack roll, roll a d6. On a 1 to 5, Asmodeus is unaffected. On a 6, Asmodeus is unaffected, and the effect is reflected back at the caster as though it originated from Asmodeus, turning the caster into the target.

Siege Monster. Asmodeus deals double damage to objects and structures.

Innate Spellcasting. Asmodeus is a level 20 spellcaster with the spellcasting ability of Charisma (spell save DC 29). He can cast all spells only using their verbal components.

Multiattack. Asmodeus will use his Frightful Presence. Then he makes five attacks: one with his bite, two with his claws, one with his horns, and one with his tail. He can use his Swallow instead of its bite.

Bite. Melee Weapon Attack: +19 to hit, reach 10 ft., one target. Hit: 36 (4d12 + 10) piercing damage. If the target is a creature, it is grappled (escape DC 29). Until this grapple ends, the target is restrained, and Asmodeus can't bite another target.

Claw. Melee Weapon Attack: +19 to hit, reach 15ft., one target. Hit: 28 (4d8 + 10) slashing damage.

Horns. Melee Weapon Attack: +19 to hit, reach 10ft., one target. Hit: 32 (4d10 + 10) piercing damage.

Tail. Melee Weapon Attack: +19 to hit, reach 20ft., one target. Hit: 24 (4d6 + 10) bludgeoning damage. If the target is a creature, it must succeed on a DC 29 Strength saving throw or be knocked prone.

Frightful Presence. Each creature of Asmodeus's choice within 120 feet of it and aware of it must succeed on a DC 21 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, with disadvantage if Asmodeus is within line of sight, 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 Asmodeus's Frightful Presence for the next 24 hours.

Swallow. Asmodeus makes one bite attack against a Large or smaller creature it is grappling. If the attack hits, the target takes the bite's damage, the target is swallowed, and the grapple ends. While swallowed, the creature is blinded and restrained, it has total cover against attacks and other effects outside Asmodeus, and it takes 56 (16d6) acid damage at the start of each of Asmodeus's turns.

If Asmodeus takes 60 damage or more on a single turn from a creature inside it, Asmodeus must succeed on a DC 29 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures, which fall prone in a space within 10 feet of the Asmodeus. If Asmodeus dies, a swallowed creature is no longer restrained by it and can escape from the corpse by using 30 feet of movement, exiting prone.

Asmodeus 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. Asmodeus regains spent legendary actions at the start of its turn. Asmodeus is a spell caster using CHA as his spell casting ability.

Attack. power word kill, feeblemind

Move. plane shift, gate

Killing Game (Costs 2 Actions). Asmodeus casts two spells at once.