Asriel Dreemurr, Absolute god of Hyperdeath and the Underground

Fragile Ego. Making a DC 20 Persuasion or Intimidation check causes Asriel to become frightened until the start of his next turn. While frightened by this or another source, Asriel has vulnerability to all damage except poison and all attacks against him have advantage.

Legendary Resistance (5/Day). If Asriel fails a saving throw, he can choose to succeed instead.

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

Magic Weapons. Asriel’s Weapon Attacks are magical.

Unearthly Recovery (1/day).  As a bonus action when Asriel fewer than half of his hit points remaining, he can regain 400 hit points.

Multiattack. Asriel makes seven attacks, using any of the attack options below in any combination

Asriel’s Pain. Ranged Spell Attack: +15 to hit, range 120 ft., one target. Hit: 8 (1d4 + 6) psychic damage.

Chaos Blaster. Ranged Spell Attack: +15 to hit, range 120 ft., one target. Hit: 8 (1d4 + 6) force damage.

Chaos Slicer. Melee Weapon Attack: +15 to hit, reach 20 ft., one target. Hit: 8 (1d4 + 6) slashing damage.

Fire Ray. Ranged Spell Attack: +15 to hit, range 120 ft., one target. Hit: 8 (1d4 + 6) fire damage.

Galacta Blazing. Ranged Spell Attack: +15 to hit, range 120 ft., one target. Hit: 8 (1d4 + 6) radiant damage.

Hyper Goner. Ranged Spell Attack: +15 to hit, range 120 ft., one target. Hit: 8 (1d4 + 6) necrotic damage.

Shocker Breaker II. Ranged Spell Attack: +15 to hit, range 120 ft., one target. Hit: 8 (1d4 + 6) lightning damage.

Spell Reflection. If Asriel makes a successful saving throw against a spell, or a spell attack misses him, he can choose another creature (including the spellcaster) he can see within 30 feet of him. The spell targets the chosen creature instead of Asriel. If the spell forced a saving throw, the chosen creature makes its own save. If the spell was an attack, the attack roll is rerolled against the chosen creature.

Asriel can take 5 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. Asriel regains spent legendary actions at the start of his turn.

Magical Missiles. Asriel fires 11 glowing darts of magical force at any targets of his choice within 120 feet. These missiles automatically hit and deal 1d4 + 1 force damage each.

Bullet Hell (Costs 2 Actions). Asriel sends a barrage of projectiles made of hellish fire at a point he can see within 60 feet. All creatures within 20 feet of this point must make a DC 23 Dexterity saving throw or take 32 (4d12 + 6) fire damage.

Angel of Death (Costs 3 Actions). Asirel assumes a terrifying form and all creatures of him choice within 60 feet of him must make a DC 23 Charisma saving throw. A creature takes 32 (4d12 + 6) psychic damage on a failed save or half as much on a successful save. A creature reduced to 0 hit points by this has its soul absorbed by Asriel.

Star Swarm (Costs 5 Actions). Stars made of magical force plummet to the ground at four different points Asriel can see. Each creature in a 40-foot-radius sphere centered on each point must make a DC 27 Dexterity Saving throw. The sphere spreads around corners. A creature takes 170 (20d12 + 40) force damage and 170 (20d12 + 40) magical bludgeoning damage on a failed save, or half as much damage on a successful one. A creature in the area of more than one sphere is affected only once.