Asriel Dreemurr, God of Hyperdeath

True Form.  After he uses the Hyper Goner action, Asriel changes into his true form.  He replaces Multiattack with Full Power Multiattack, and cannot use Hyper Goner action even if it recharges.  While in his true form, he regains 40 hitpoints at the beginning of his turn.  His true form fades when he is out of initiative count.

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

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

Unearthly Attacks.  Asriel's attacks are magical, and targets of his attacks cannot benefit from cover.

Energy Conversion.  When Asriel takes fire, lighting, or cold damage, he regains 5d10 hit points.  If he is subjected to an effect that deals force damage, he can choose to turn the effect against the originating creature.

Titanic Power (True Form Only).  When a creature that starts its turn within 5 feet of him must succeed on a DC 27 Constitution saving throw or be pushed back 20 feet, take 2d8 force damage, and be knocked prone. 

Multiattack (Regular Form Only).  Asriel makes either four Chaos Saber attacks, three Galacta Blazing attacks, five Shocker Breaker attacks, or one Havok Blaster.  He can then use his Hyper Goner if it is ready.

Full Power Multiattack (True Form Only).  This Multiattack cannot be used until Asriel uses the Hyper Goner attack.  Asriel uses five Angel of Death attacks.

Hyper Goner (Regular Form Only, Recharge 19-20).  Asriel creates a phantasmic skull of destruction that fires a beam of death in a 120-foot cone originating from a him.  Any creatures in the area must succeed on a DC 27 Constitution saving throw, taking 195 (30d12) force damage on a failed save, and half on a successful one.  Asriel starts a battle needing to recharge Hyper Goner.

Chaos Sabers (Regular Form Only).  Melee Weapon Attack: +19 to hit, range 10 ft., one target. Hit: 17 (2d6 + 10) slashing and 6 (1d12) force damage.

Shocker Breaker (Regular Form Only).  Asriel sends a bolt of electricity arcing from the sky at a destination he can see within 120 feet of him.  Creatures in a 10-foot radius of the lightning strike must make a DC 27 Dexterity saving throw.  On a failed save, a creature takes 14 (4d6) lightning damage and is knocked prone.

Galacta Blazing (Regular Form Only).  Asriel summons a small star crashing into the ground at a point he can see within 120 feet of him.  Creatures in a 20-foot radius of the star must make a DC 27 Dexterity saving throw.  On a failed save, the creature takes 16 (5d6) bludgeoning damage and 13 (3d8) radiant damage.  On a success, the creature takes half damage

Havok Blaster (Regular Form Only).  Ranged Weapon Attack: +19 to hit, range 1000 ft., one target. Hit: 42 (5d12 +10) damage.  The damage is determined by rolling a d10.

1. Lightning
2. Acid
3. Necrotic
4. Radiant
5. Fire
6. Cold
7. Thunder
8. Psychic
9. Force
10. Poison

On a hit, the target must make a DC 27 Constitution saving throw or gain one of the following conditions until the end of its next turn.  The condition is determined by rolling a d6.

1. The target is blinded.
2. The target is stunned.
3. The target is frightened.
4. The target is petrified. 
5. The target is paralyzed.
6. The target is poisoned.

Angel Of Death (True Form Only).  Asriel points his finger at one creature he can see within 120 feet and unleashes a barrage of power.  The creature takes 20 force damage.

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.

Asriel uses these legendary actions when he isn't in his true form.

Galacta Blazing (Costs 2 Actions).  Asriel uses the Galacta Blazing attack.

Shocker Breaker.  Asriel makes a Shocker Breaker attack.

Dervish (Costs 3 Actions).  Asriel makes two Chaos Saber attacks.

Havok Blaster (Costs 4 Actions).  Asriel uses the Havok Blaster attack.

Asriel uses this legendary action while he is in his true form.

Angel Of Death.  Asriel uses the Angel Of Death attack.