Anguish Soul (Mythic Trait; Recharges after a Short or Long Rest). If Abaddon is reduced to 0 hit points, he doesn’t die or fall unconscious. Instead, his body falls apart into several dark energetic orbs that represent his last life force. This orbs will invade all hostile creatures in a 120ft. radius and pierce into their brains, where they will trigger an inner fight between the creature and Abaddon Soul Splinter (monster).

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

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

Abaddons’s Lair

Abaddon was banished to his own realm by the prime gods and is chained there in the center. He has conjured up 4 energy pylons around him, which absorb the energy of the realm and serve as the source of his growing power. Each pylon increases Abaddon's armor class by 2 and gives him immunity to one damage type (fire, lightning, ice, radiant). Only when all 4 pylons are destroyed at the same time, Abaddon can be defeated (AC is lowered to 18, no more immunities). As long as at least 1 pylon is still standing, destroyed pylons regenerate after 4 turns.

• each pylon has 30 hit points and is resistant to bludgeoning, slashing and piercing damage.

Lair Action

On initiative count 20 (losing initiative ties), Abaddon can take a lair action to cause one of the following effects. He can’t use the same effect two rounds in a row.

• Abaddon can spawn as many Margonites as there are active pylons. He can choose any combination of Margonite Brute (melee), Margonite Pierce (ranged), Margonite Scourge (mage), Margonite Dread (necromancer)

Multiattack. Abaddon makes four attacks with his claws.

Claws. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit:  (6d6) slashing damage.

Growing Pain. On the start of each of his turns Abaddons gets a pain point if he was hit by a Spell or Weapon Attack since his last turn. When he reaches 5 pain points he immediately unleashes the pain and every creature in a 30 ft. radius has to make an DC 17 Dexterity saving throw. On a failed save the creature takes 8d6 necrotic damage, 8d4 force damage and is pushed away from Abaddon 10 ft.

Abaddon can take 3 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. Abaddon regains spent legendary actions at the start of his turn.

Claws. Abaddon makes one attack with his claws.

Veil of Sorrow. Abaddon makes a breath attack. Any creature in a 15 ft. cone has to make a DC 16 Dexterity saving throw. On a failed save the creature is blinded.

If Abaddon'y mythic phase is activated, his remaining life forces tries to infest surrounding hostile creatures to suck their souls and manifest his energy again in a living form. Therefore his remaining life force splits into several Abaddon Soul Splinters that trigger an inner fight in the infested creature. Since these fights happen in their subconscious the creatures are at full capacity of any of their ressources (like spell slots) and gain back all of their hit points (only as long as they remain in their subconscious).

If the majority of splinters manage to defeat creatures and suck their souls, Abaddon can reincarnate in a living body starting to invade the world with his margonite army.

If the majority of splinters are defeated in the inner fight, the remaining life force is too weak to sustain and all remaining splinters decay and their fights end immediately.