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

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

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

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

Magic Weapons. Brathkal's weapon attacks are magical.

Multiattack. Brathkal makes three melee attacks.

Greataxe. Melee Weapon Attack: +19 to hit, reach 10 ft., one target. Hit: 36 (4d12 + 10) slashing damage.

Fire Breath (Recharge 5-6). Brathkal exhales fire in a 90-foot cone. Each creature in that area must make a DC 17 Dexterity saving throw, taking 94(21d8) fire damage on a failed save, or half as much damage on a successful one.

Brathkal 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. Brathkal regains spent legendary actions at the start of its turn.

Detect. Brathkal makes a Wisdom (Perception) check.

Move. Brathkal moves up to half its speed.

Quake (Costs 2 Actions). Brathkal stops its feet which causes an earthquake.. Each creature within 50 feet of Brathkal must succeed on a DC 17 Dexterity saving throw or  be knocked prone.