Armageddon

Legendary Resistance(7/per day).  If Armageddon fails a saving throw, it can choose to succeed it instead.

Limited Magic Resistance.   Unless it wishes to be affected, Armageddon is immune to spells o f 4th level or lower. It has advantage on saving throws against all other spells and magical effects.

Magic Weapons.  Armageddon's weapons are magical.

Regeneration.  Armageddon regains 50 hit points each round.

Ultimate Being.  Armageddon cannot be damaged by a creature that isn't a Tarrasque or a deity. 

Multiattack. Armageddon can attack with the short swords 4 times, the great axe two times, or the long sword 2 times.  Armageddon can also cast one cantrip along with attacking with either the great axe or long sword.

Spellcasting. Armageddon is a 20th-level spellcaster. Its spellcasting ability is (DC=26, +18 spell attack bonus). Armageddon has following spells prepared:
Cantrips (at will): [Armageddon's Arrow], [Cataclysmic slam], [Raise thy Sword]
2nd level (5 slots): [moon beam]
7th level (3slots): [prismatic spray]
9th level (1 slot): [meteor swarm]

Copy.  Armageddon makes two copies of itself, both of which has a 17 ac, and 50 hp, and only copies actions that the original Armageddon does.  They also move parallel with the original Armageddon, and go away after the start of Armageddon's next turn or if their HP hit 0.  Only two copies can be out at a time, and this ability can only be activated every four rounds, and only be activated as a bonus action. 

Weapon Conjuring.  Armageddon can switch between a great axe, two short swords, or a long sword with shield.  This change can only happen once per round, and Armageddon will automatically unsummon weapons in order to cast spells.

Short Sword. Melee Weapon Attack: +19 to hit, reach 10ft., 1-2 target. Hit: 20(3d8 + 10) [force and slashing] damage. 

great axe. Melee Weapon Attack: +19 to hit, reach 15 ft, 1 target. Hit 32(3d12+10) [force and slashing] damage

Long Sword. Melee Weapon Attack: +19 to hit, reach 15 ft, 1 target. Hit 30(3d10+10) [force and slashing] damage.

Reaction Name. Enter the description for your action.

Armageddon can take 7 legendary actions, choosing from the options below. Armageddon regains spent legendary actions at the start of her turn

Force Slice (Costs 2 Actions). Armageddon swings their weapon, causing damage based on their current weapon in a 60 foot line with a width of 20 ft.  This deals damage to all of those whose AC's or less than the attack roll, and the damage is the weapon's attack role + 10 force damage.

Blast of Positive Armageddon (costs 3 actions).  Armageddon summons three blasts of light around her head that target three 10 ft radius areas, in which each creature in those three areas must make a dex saving check with a DC(20).  each creature that fails gets dealt 10d8 radiant damage, and each creature that succeeds gets dealt half of that.

Aura of Negative Armageddon (costs 3 actions).  Armageddon summons a aura with a 30 ft radius, in which each creature in that area must make a dex saving check with a DC(20).  each creature that fails gets dealt 8d10 necrotic damage, and each creature that succeeds gets dealt half of that.