Chernobog, God of the Damned

Immutable Form. Chernobog is immune to any spell or effect that would alter its form.

Empowered Attacks. Chernobog's attacks are considered magical.

Legendary Resistance (3/day). If Chernobog fails a saving throw, he can choose to succeed instead.

Turn Immunity. Chernobog is immune to effects that turn undead.

Undead Nature. Chernobog doesn't need to eat, sleep, or drink, and is immune to poison and disease.

Death Throes. When Chernobog is reduced to 0 hit points, it explodes into a shower of blood and gore. Each creature within 30 feet of Chernobog that has <75% of its total hit points is subjected to the effects of Chernobog's Corrupt Wounds action, except that they cannot remake the saving throw. The poisoned condition ends when the creature is cured with a lesser restoration spell or similar magic. 

Formation Beyond Death (Mythic Trait; Recharges after a Short or Long Rest). If Chernobog is reduced to 0 hit points, he doesn't die or fall unconscious. Instead, he regains 275 hit points and 75 temporary hit points. While Chernobog has temporary hit points, he has resistance to all damage. In addition, the bones and flesh comprising his body fall apart, and he re-forms in an unoccupied location within 50 feet of his previous location. This does trigger his Death Throes ability.

Multiattack. Chernobog makes two Malignant Hammer attacks.

Malignant Hammer. Melee Weapon Attack: +13 to hit, reach 10 ft., one target. Hit: 28 (5d8 + 6) bludgeoning damage. The target must succeed on a DC 21 Constitution saving throw or take an additional 14 (2d10 + 3) necrotic damage.

Swallow Undead. Chernobog targets an undead creature within 5 feet of him. The creature instantly dies, and is unable to be resurrected except by a wish spell. Chernobog regains a number of hit points equal to the twice the number of hit dice that creature has + 7.

Corrupt Wounds. Chernobog chooses one creature that damaged him during the current round and is not at maximum hit points. It must make a DC 21 Constitution save or take 22 (4d10) poison damage and be poisoned for 1 hour. They may remake the save at the end of each of their turns, ending the poisoned condition on a success. Constructs and undead creatures ignore this effect.

Command Undead. As a reaction, Chernobog can command one undead creature within 15 feet of him and allow it to make an attack roll.

Chernobog 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. Chernobog regains spent legendary actions at the start of his turn.

Melee Attack. Chernobog uses Swallow Undead or makes one melee attack with his Hammer.

Assemble Undead (Costs 2 Actions). Any amount of Undead creatures whose Challenge Ratings are less than or equal to 5 appear in unoccupied spaces within 30 feet of Chernobog and not behind total cover.

If Chernobog's mythic trait is active, it can use the options below as legendary actions for 1 hour after using his Formation Beyond Death ability.

Battle Stomp. Chernobog stomps the ground, shaking the earth heavily. Each creature within 15 feet of him must make a DC 17 Strength or Dexterity save (their choice) or fall prone.

Summon Devil (Costs 3 Actions). Chernobog summons two Barbed Devils at a location within 30 feet of him. You may choose different locations for the devils.