Fire Absorption. Whenever BT is subjected to fire damage, it takes no damage and instead regains a number of hit points equal to the fire damage dealt.
Immutable Form. BT is immune to any spell or effect that would alter its form.
Magic Resistance. BT has advantage on saving throws against spells and other magical effects.
Magic Weapons. BT's weapon attacks are magical.
Pilotable Construct. A creature can board and pilot BT. However BT has its own agency and can oppose the piloting creatures reaction if it feels obligated to do so.
Multiattack. BT makes two melee attacks.
Slam. Melee Weapon Attack: +13; to hit, reach 5 ft., one target. Hit: 20 bludgeoning damage.
Avernus Wasteland Arc Cannon. ranged Weapon Attack: +10;to hit, reach 30ft / 150 ft., one target. Hit: 23 (3d12 ); Lightning damage. Creatures within 20ft of the targeted creature must succeed a DC18 Constitution Saving Throw or suffer 3d12 lightning damage or half on a successful roll.
Breath Of The Styx (Recharge 6). BT exhales the poisonous fumes from the river Styx in a 15-foot cone. Each creature in that area must make a DC 19 Constitution saving throw, taking 45 poison damage on a failed save, or half as much damage on a successful one.