Armored Fire King

If you can't take the heat... If Armored Fire King is fought in an enclosed space, at the top of initiative each creature present that is not immune to fire must make a Constitution Saving Throw equal to 8+(Rx2), where R is the number of rounds that have passed since the room had become sealed. On a failed save, the creature gains 1 level of exhaustion.

Multiattack. The Armored Fire King makes three attacks, using Boost Strike or Vent Burst in any combination.

Boost Strike. The Armored Fire King moves up to half its Speed straight toward an enemy it can see without provoking Opportunity Attacks. He then makes a Melee Attack Roll: +9, reach 5 ft. Hit: 19 (4d6 + 5) Bludgeoning damage. The warrior also creates the following effect:

Sap. The target has Disadvantage on its next attack roll before the start of the Armored Fire King’s next turn.

Vent Attack. Ranged Attack Roll: +9, range 50/300 ft. Hit: 18 (3d8 + 5) Fire damage, and the target’s Speed decreases by 10 feet until the end of the target’s next turn. This de-buff stacks with itself.

Vent Burst (Recharge 5-6). Armored Fire King vents his built up heat in all directions. Dexterity Saving Throw: DC 16, each creature in a 10-foot Emanation originating from Armored Fire King. Failure: 21 (6d6) Fire damage. Success: Half damage.

Evasive Approach. Trigger: Armored Fire King is hit by an attack roll. Response: Armored Fire King moves up to half his Speed straight toward an enemy it can see without provoking Opportunity Attacks, avoiding the attack in the process.

Has 3 legendary Actions per turn.

Trading Blows. If Armored Fire King is hit by a melee attack roll from within 5ft of him, Armored Fire King takes the maximum damage from this attack, and then makes one Boost Strike against the attacker, dealing maximum damage on hit.