Absorption. Whenever the abyssal war machine is subjected to fire damage or damage from an evil aligned creature, it takes no damage and instead regains a number of hit points equal to the damage dealt.

Immutable Form. The abyssal war machine is immune to any spell or effect that would alter its form.

Innate Spellcasting. The abyssal war machine’s innate spellcasting ability is Constitution. The abyssal war machine can innately cast the following spells (spell save DC 27, +19 to hit with spell attacks) as abilities, requiring no material components. Casting as an ability means they are treated as a natural attack rather than a spell for the purposes of countering or features.

At will: fire bolt, control flames
5/day each: burning hands, flaming sphere, scorching ray
3/day each: fireball, flame strike
1/day each: fire storm, immolation, incendiary cloud

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

Magic Resistance. The abyssal war machine has advantage on saving throws against spells and other magical effects.

Magic Weapons. The abyssal war machine’s weapon attacks are magical.

Siege Monster. The abyssal war machine deals double damage to objects and structures.

Multiattack. The abyssal war machine makes five melee attacks, it may trade two melee attacks for another action.

Claws. Melee Weapon Attack: +19 to hit, reach 15 ft., one target. Hit: 32 (4d10+10) slashing damage.

Tail Whip. Melee Weapon Attack: +19 to hit, reach 25 ft., one target. Hit: 28 (4d8+10) bludgeoning damage. The target must make a DC 20 Dexterity saving throw or become grappled. Only one target can be grappled at a time in this way.

Tail Jab. Melee Weapon Attack: +19 to hit, reach 25 ft., one target. Hit: 32 (4d10+10) piercing damage. The abyssal war machine forces the target to make a DC 20 Strength saving throw or become impaled on the tail and restrained. On its next turn, the abyssal war machine may rip its tail barb from a target restrained in this way dealing an additional 22 (4d10) piercing damage.

Smash. Melee Weapon Attack: +19 to hit, reach 15 ft., one target. Hit: 36 (4d12+10) bludgeoning damage.

Grasping Hands. Melee Weapon Attack: +19 to hit, reach 15 ft., one target. Hit: 32 (4d10+10) piercing damage. The target must make a DC 20 Dexterity saving throw or become grappled, only two targets at a time can be grappled in this way.

Impaling Fate. The abyssal war machine forces a grappled or restrained creature to make a DC 20 Strength saving throw, on a failure the target takes 50 (10d10) piercing damage and is partially impaled on the abyssal war machine’s spike and is considered restrained. On each of its following turns as a bonus action the abyssal war machine can force the same check to further impale the target. After 3 failures the target is fully impaled and takes disadvantage on any attempts to get free. A creature restrained in this way may use their action to make a DC 20 Strength saving throw to become free, if successful they are no longer restrained. The abyssal war machine can have up to 3 creatures restrained in this way.

Crown of Souls (Recharge 6). The abyssal war machine casts crown of stars, appearing as burning souls floating around its head and doing force damage.

Super Heated (Recharge 6). The abyssal war machine shoots out fire from its plated body forcing targets within a 30 foot radius to make a DC 20 Dexterity saving throw taking 90 (15d12) fire damage on a failure, or half as much on a success.

The abyssal war machine can take 5 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. The abyssal war machine regains spent legendary actions at the start of its turn.

Big Squeeze. The abyssal war machine may squeeze any target grappled by its tail for 44 (8d10) piercing damage, the target must then make a DC 22 Constitution saving throw or take an additional 18 (4d8) fire damage.

Crushing Slam. The abyssal war machine strikes the ground forcing targets within a 60 foot radius to make a DC 20 Dexterity saving throw taking 52 (8d12) force damage and flying back 15 feet before being knocked prone, on a save the target only takes half damage.

Line in the Fire. The abyssal war machine casts aganazzar’s scorcher.

Quickened Guardian (Costs 2 Actions). The abyssal war machine casts steel wind strike.

Faster Reheat (Costs 2 Actions). The abyssal war machine instantly recharges and uses the Super Heated attack.

Focused Crushing Slam (Costs 3 Actions). The abyssal war machine can focus all of the Crushing Slam action on a single target, doubling the damage of the attack and forcing disadvantage on the Dexterity saving throw.

Soul Meal (Costs 5 Actions). The abyssal war machine can begin to consume a grappled or restrained creature making a grasping hands attack. If the attack hits, the target takes the grasping hand’s damage, the target is shoved into the abyssal war machine’s burning core, and the grapple ends. While trapped in the burning core, the creature is blinded and restrained, it has total cover against attacks and other effects outside the abyssal war machine, and it takes 56 (16d6) fire damage at the start of each of the abyssal war machine’s turns. If the target is a creature or a flammable object, it ignites. Until a creature takes an action to douse the fire, the target takes 5 (1d10) fire damage at the end of each of its turns. The creature will reignite at the start of the abyssal  war machine’s turn.
If a creature dies inside of the abyssal war machine’s burning core their soul is consumed and their body becomes ash. The target can not be brought back except with a wish spell or similar magic. After consuming a soul the abyssal war machine regains the max HP of the soul consumed.