Molten Reactor Core.

Creatures that start their turn within 15 feet of Vulkran-Khaz take 4d6 fire damage.

Immutable Form. Vulkran-Khaz is immune to any spell or effect that would alter its form.

Living Forge Engine: When Vulkran-Khaz is reduced below half its hit points, its attacks deal an extra 2d10 Fire Damage

Legendary Resistance (3/Day).
If Vulkran-Khaz fails a saving throw, it can choose to succeed instead.

Fire Absorption. Whenever the golem is subjected to fire damage, it takes no damage and instead regains a number of hit points equal to the fire damage dealt.

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

Magic Weapons. The golem's weapon attacks are magical.

Multiattack: Slam x2 + Forge Beam (if available)

Slam:
+14 to hit, 3d12+8 bludgeoning + 3d10 fire, STR save or knocked prone

Forge Beam (Recharge 5–6):
60-ft line, Dex save, 8d10 fire + 6d10 radiant damage

Anvil Pulse (Recharge 4–6):
30-ft radius quake, Dex save or 6d10 fire damage + prone

Soulforge Brand (1/day):
Target takes double fire damage and glows with a 20' radius (cannot become invisible, advantage to attacks to hit this target)

Ignite the Forges.
One creature Vulkran-Khaz can see within 30 feet must make a DC 20 Dexterity saving throw, taking 4d10 fire damage, or half as much on a successful save.

Summon Forgeborn (Recharge 6);
Vulkran-Khaz summons one Forgeborn Acolyte or one Magma Mephit in an unoccupied space within 30 feet.

Molten Retaliation.
When a creature hits Vulkran-Khaz with a melee attack, that creature takes 4d8 fire damage.

Deflect the Unworthy.
When a creature misses Vulkran-Khaz with a melee attack, Vulkran-Khaz can force that creature to make a DC 20 Strength saving throw or be pushed 15 feet and knocked prone.

Vulkran-Khaz can take 3 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature’s turn.

Hammer Step.
Vulkran-Khaz moves up to half its speed without provoking opportunity attacks.

Scalding Backhand.
Vulkran-Khaz makes one Slam attack.

Furnace Roar (Costs 2 Actions).
Each creature of Vulkran-Khaz’s choice within 30 feet must make a DC 20 Wisdom saving throw or become frightened until the end of its next turn.

Ignite the Forge (Costs 3 Actions).
Vulkran-Khaz uses Summon Forgeborn or regains the use of Forge Beam.

PHASE 3 – MYTHIC FORM: CORE MELTDOWN (100 HP)

Mythic Trait: Crucible Overload

When Vulkran-Khaz is reduced to 0 hit points, it instead explodes in molten light and regains 200 hit points. All creatures within 60 feet take 10d8 fire damage.

The battlefield becomes unstable:

• Lava floods 10 ft per round

• One Fire Elemental spawns each round

• All terrain becomes difficult terrain