Azrifel, of Eternities' End

Innate Spellcasting: Azrifel's Innate Spellcasting ability is Intelligence (Spell Save DC 22). They can cast the following spells, requiring no components.

At Will: Divine Smite (4th Level), Magic Missile (6th Level)

Three Turn Cooldown: Teleport (7th Level), Sunburst (8th Level)

Thrice Per Day: Counterspell (9th Level), Power Word Stun (8th Level), Black Tentacles (4th Level)

Twice Per Day: Mordenkainen's Sword (7th Level), Mordenkainen's Faithful Hound (4th Level)

Once Per Day: Time Stop (9th Level)

Cosmic Eternity: Azrifel can take an additional action on each of their turns, cast Teleport as a reaction and their time stop spell always lasts the maximum number of turns. Azrifel Regenerates 1D10 +10 Hit Points at the end of each of their turns and takes 25 less damage from all attacks, after resistances have applied.

Eternities' End: Azrifel's attacks have a chance to ignore resistances and hit through immunities. Whenever Azrifel Makes an attack, roll a D20. On a roll of 16 or higher, the attack treats all resistances as though they were neutral and all immunities as though they are resistances.

Relentless Assault: If the first attack roll of Azrifel's Multiattack is with a Spatial Rend, and it lands a critical hit, the next attack against that creature Azrifel makes has advantage. Whenever Azrifel reduces a creatures' Hit Points to 0, they may spend a bonus action to immediately make an attack against the next nearest creature.

Legendary Resistance: Thrice per day, if Azrifel fails a saving throw, they may choose to succeed instead.

Final Stand: Once per day, when Azrifel's Hit Points are reduced to 0, they gain 200 Temporary Hit Points and become Corrupted. While Corrupted, Azrifel's Divine Smite and Magic Missile become 9th Level, their flying speed is tripled, their dexterity score becomes 40, their armor class is reduced to 10, all attacks made against them get disadvantage, they lose all resistances and become vulnerable to all damage types. Additionally, while Corrupted, Azrifel loses Cosmic Eternity's Hit Point Regeneration, as well as all attacks that hit Azrifel are treated as critical hits and ignore Cosmic Eternity's Damage Reduction.

Multiattack: Azrifel makes two attacks, Either with any combination of two Spatial Rend attacks, any two different offensive spells, or a Spatial Rend and an Offensive Spell.

Spatial Rend - Angelic: Azrifel makes an attack with the Ballad of Heavensong and Angelfire, using one of its custom attacks.

Spatial Rend - Demonic: Azrifel makes an attack with the Ballad of Brimstone and Balefire, using one of its custom attacks.

Cosmic Collapse: Azrifel takes damage equal to one fifth of their remaining Hit Points, rounded up, then casts Four Magic Missile (6th Level) spells. (Two Actions)

Phase Breach: Azrifel takes 2D12 Force Damage (Unaffected by Cosmic Eternity), moves behind a medium or smaller creature within 120ft, the creature then makes a DC 20 Dexterity saving throw. On a failed save, the creature takes 3D4 Necrotic Damage and 3D4 Radiant Damage and is lifted off the ground by the neck and restrained. A creature restrained this way cannot make actions until they are no longer restrained. On a restrained creatures turn, that creature may make a DC 19 Strength saving throw. On a successful save, they are no longer restrained and fall to the ground.

Azrifel may take 5 Legendary Actions, once per turn at the end of any other creatures turn. 

Null Strike - Azrifel makes any Spatial Rend attack, but the damage is treated as though it were Force Damage and is reduced by 25% after initial damage calculation.

Teleport - Azrifel may cast the Teleport spell as a Legendary Action.