Asmodeus, Lord of the Nine Hells

Infernal Rebirth (Recharges after a Short or Long Rest). If Asmodeus would be reduced to 0 hit points, his current hit point total instead resets to 500 hit points, he recharges his Grasp of Hell, and he regains any expended uses of Legendary Resistance. Additionally, Asmodeus can now use the options in the “Mythic Actions” section for 1 hour. Award a party an additional 155,000 XP (310,000 XP total) for defeating Asmodeus after his Infernal Rebirth activates.

Discorporation. When Asmodeus dies, his body is destroyed but his essence travels back to his domain in the Nine Hells, and he is unable to take physical form for a time.

Devil’s Sight. Magical darkness doesn’t impede Asmodeus's darkvision.

Limited Magic Immunity. Unless he wishes to be affected, Asmodeus is immune to spells of 5th level or lower. He has advantage on saving throws against all other spells and magical effects.

Fiery Weapons. Asmodeuss’s weapon attacks are magical. When he hits with any weapon, the weapon deals an extra 36 (8d8) fire damage (included in the weapon attacks below).

Innate Spellcasting. Asmodeus’s innate spellcasting ability is Charisma (spell save DC 26). He can innately cast the following spells, requiring no material components:

At will: alter self (can become Medium when changing his appearance), detect evil and good, fireball, wall of fire, hellish rebuke (as a 4th level spell)

3/day each: blade barrier, dispel evil and good, finger of death, divine word, power word pain, harm, dispel magic

1/day each: reality break, meteor swarm, power word: kill, dominate monster

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

Regeneration. Asmodeus regains 30 hit points at the start of his turn. If he takes radiant damage, this trait doesn’t function at the start of his next turn. Asmodeus dies only if he starts his turn with 0 hit points and doesn’t regenerate.

Multiattack. Asmodeus can cast a spell or use Grasp of Hell. He then makes three melee attacks.

Godbreaker. Melee Weapon Attack: +17 to hit, reach 10 ft., one target. Hit: 17 (3d8 + 8) bludgeoning damage, plus 36 (8d8) fire damage.

Grasp of Hell (Recharge 5–6). Asmodeus touches one creature within 10 feet of him. The target must succeed on a DC 26 Constitution saving throw or take 44 (8d10) fire damage and be poisoned for 1 minute. While poisoned in this way, the target is also blinded and deafened. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. Fire damage from this attack ignores immunity, treating it as resistance instead.

Teleport. Asmodeus magically teleports, along with any equipment he is wearing or carrying, up to 120 feet to an unoccupied space he can see.

Asmodeus can take up to three reactions per round but only one per turn.

Dark One's Own Luck. In response to being hit by an attack, Asmodeus can use his reaction to force the targeting creature to reroll, subtracting 1d4 from the roll.

Infernal Gateway. In response to being targeted by a spell, Asmodeus teleports 60 feet in any direction. If his new location is out of the range of the spell, then the spell fails.

Hellish Aborption. When a creature that Asmodeus can see within 120 feet of him casts a spell, he can use his reaction to siphon the spell's mana into himself. The spell fails, and Asmodeus regains a number of spell slots of any level with a total value equal to half the spell's level.

Asmodeus 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. Asmodeus regains spent legendary actions at the start of his turn.

Immolating Gaze (Costs 2 Actions). Asmodeus turns his magical gaze toward one creature he can see within 120 feet of him and commands it to combust. The target must succeed on a DC 26 Wisdom saving throw or take 22 (4d10) fire damage.

Teleport. Asmodeus uses his Teleport action.

Infernal Arcana. Asmodeus casts a spell from his Innate Spellcasting list.

If Asmodeus's Infernal Rebirth trait has activated in the last hour, he can use the options below as legendary actions.

Infernal Consumption (Costs 2 Actions). Asmodeus targets a creature he can see within 50 feet of him. The target must make a DC 26 Wisdom saving throw or take (4d10) necrotic damage, or half as much on a failure. On a failed save, the creature's hit point maximum is reduced by an amount equal to the necrotic damage it took for one hour. Asmodeus regains hit points equal to the amount of damage dealt.

Summon Underlings (Costs 3 Actions). Asmodeus summons any number of devils with a total CR of 8. These devils appear in a space Asmodeus can see within 100 feet of him, and they are loyal to Asmodeus. The summoned devils roll their own initiative. While these devils are alive, Asmodeus cannot use this legendary action. After the devils are either slain or leave, roll a d6  at the start of each of Asmodeus's turns. On a 6, Asmodeus regains use of this ability.