Avatar of Khaine

Siege Monster. The avatar of khaine deals double damage to objects and structures.

Fear Aura. Any creature hostile to the avatar that starts its turn within 20 feet of the avatar must make a DC 20 Wisdom saving throw, unless the avatar is incapacitated. On a failed save, the creature is frightened until the start of its next turn. If a creature's saving throw is successful, the creature is immune to the avatar's Fear Aura for the next 24 hours.

Magic Weapons: The avatar's weapon attacks are magical.

Magic Resistance: The avatar has advantage on saving throws against spells and magical effects.

Fiery Form: A creature that starts its turn within 5 feet of the avatar takes 7 (2d6) fire damage.

Innate Spellcasting. The avatar can cast the following spells without expending spell components. The avatar's innate spellcasting ability is Wisdom (spell save DC 20, +12 to hit with spell attacks). 
At will: fireball, wall of fire,  fire shield.

3/day each: flame strike, sunbeam, globe of invulnerability.  

1/day each: earthquake, sunburst

Burning Spirit (Mythic Trait, Recharges after a Short or Long Rest). When the avatar of khaine is reduced to 0HP it does not die or fall unconscious. Instead, the avatar's armour sloughs off, revealing the blazing form beneath. The avatar regains 220 Hit Points, lowers their AC to 15, and gains the following traits:

Blazing Form (replaces Fiery Form). Any creature that starts its turn within 15 feet of the avatar takes 52 (15d6) fire damage.

Berserk Rage. The avatar gains advantage on all attack rolls they make.

Combusting Doom. The avatar can use its Fiery Beam action as a Bonus Action.

Multiattack. The avatar makes five attacks, choosing from the options below.

Wailing Doom. Melee Weapon Attack: +18 to hit, reach 10 ft., 1 target. Hit: 32 (4d10 + 10) piercing damage plus 10 (3d6) fire damage.

Wailing Doom. Ranged Weapon Attack: +13 to hit, range 60/120 ft., 1 target. Hit: 32 (4d10 + 10) piercing damage plus 10 (3d6) fire damage.

Bloody Fist. Melee Weapon Attack:  +18 to hit, reach 5 ft., 1 target. Hit: 28 (4d8 + 10) bludgeoning damage. The target must succeed on a DC 20 Wisdom saving throw or succumb to Blood Madness for 1 hour. While succumbed in this way, creatures affected see all creatures, friend or foe, as targets of their rage, and will attack anyone they come across, regardless if they are hostile to them or not. The affected creature can repeat the saving throw each time they take damage and at the end of each of their turns.

Fiery Beam. The avatar shoots a blast of fire from the wailing doom that is 5 feet wide and 60 feet long. Each creature in the line must make a DC 20 Dexterity saving throw, taking 55 (10d10) fire damage on a failed save, and half as much on a successful one.

The avatar of khaine has 3 legendary actions.

Attack (Costs 1 Action). The avatar makes an attack.

Fiery Beam (Costs 1 Action). The avatar uses its Fiery Beam.

Detect (Costs 1 Action). The avatar makes a Wisdom (Perception) Check.

If the avatar's mythic trait is active, it can use the options below as legendary actions for 1 hour after using Burning Spirit.

Swirling Blaze (Costs 2 Actions). Every creature within 10 feet of the avatar must make a DC 18 Dexterity saving throw or take 32 (4d10 + 10) slashing damage plus 17 (5d6) fire damage.

Fire Stomp (Costs 2 Actions). Each creature within 5 feet of the avatar must make a dc 26 Strength saving throw or be pushed back 10 feet and knocked prone.