Archaon the Everchosen

Blessing of Khorne. Archaon’s melee weapon attacks score a critical hit on a roll of 18-20  If Khorne’s portal has been sealed, his attacks instead critically hit on 19-20.

Blessing of Tzeentch. When Archaon is targeted by a spell or magical effect, roll a d6. On a roll of 5-6, Archaon suffers no effect and the caster suffers the same effect instead, if applicable. If Tzeentch’s portal has been sealed, this effect only triggers on a 6.

Blessing of Nurgle. Archaon regains 40 hit points at the start of his turn if he has at least 1 hit point remaining. If Nurgle’s portal has been sealed, he instead regains 20 hit points.

Blessing of Slaanesh. Archaon has two reactions per round and when a creature misses him with an attack he may move up tohalf his speed without provoking opportunity attacks. If Slaanesh’s portal has been sealed, he instead hasone reaction per round. 

Chaos Undivided. While all four blessings remain active, Archaon gains+2 AC and +2 to all saving throws.  If any portals have been closed, this ability does not apply.

Armour of Morkar. Archaon has resistance to all damage except force, radiant, and psychic damage.

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

Aura of Ruin. Creatures of Archaon’s choice within 60 feet take 10 psychic damage at the start of their turns and have disadvantage on saving throws against being frightened.

Magic Weapons. Archaon’s weapon attacks are magical.

Innate Spellcasting. Archaon’s spellcasting ability is Charisma (spell save DC 24, +16 to hit with spell attacks). He casts the following spells innately, requiring no components. While Archaon has half his hit points or more, his concentration cannot be broken.

At will: counterspell, dispel magic, darkness

3/day each: disintegrate, wall of force, power word stun

1/day each: meteor swarm, maze, time stop

Multiattack. Archaon makesthree attacks, each of which can be eitherSlayer of Kings or Chaos Bolt. He may replace one attack with casting an innate spell.

Destined End. Once per turn when Archaon scores a critical hit, he may immediately make one additional Slayer of Kings attack.

Slayer of Kings. Melee Weapon Attack: +17 to hit, reach 5 ft., one target. Hit: 4d8+9 slashing plus 3d10 force damage.

Chaos Bolt. Ranged Spell Attack: +15 to hit, range 120 ft., one target. Hit: 6d10 damage. Roll a d8 to determine the damage type:
1 Acid
2 Cold
3 Fire
4 Force
5 Lightning
6 Necrotic
7 Psychic
8 Thunder

Balefire Blast (Recharge 5–6). Archaon unleashes a beam of warpfire in a120-foot line that is 5 feet wide. Creatures in the line must make a DC 24 Dexterity saving throw, taking 10d12 fire damage on a failure or half as much on a success

Archaon 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.

Attack. Archaon makes one Slayer of Kings attack.

Dread Command (Costs 2 Actions). Creatures of Archaon’s choice within 30 feet must succeed on a DC 24 Wisdom saving throw or become frightened until the end of their next turn.

Balefire Surge (Costs 3 Actions). Archaon releases a blast of warpfire in a60-foot cone. Creatures must make a DC 24 Dexterity saving throw, taking 10d10 fire damage on a failure or half damage on a success.

The Everchosen Endures. When Archaon is reduced to 0 hit points, he instead regains 400 hit points and enters his mythic phase.

While in this phase, Archaon gains resistance to Radiant damage, and all of the Blessings are no longer considered to be Diminished.

Reality Rend (Costs 3 Actions). A rift tears open at a point within 120 feet. Creatures within 30 feet must make a DC 24 Constitution saving throw, taking 15d12 force damage on a failure or half damage on a success. Creatures that fail the save are pulled 10 feet toward the center.

Daemonic Resurgence (Costs 2 Actions). Archaon can regain one of the once per day spells he had cast previously.