Legendary Resistance. (3/day) If Abaddon would fail a saving throw he can choose to succeed instead.

Telepathy. 60 ft. reach

Attack Action. During each attack Abaddon attacks once with his Tail, twice with his Wings, and twice with his Claws.

Wings Attack. Melee Weapon Attack: +8 to hit, reach 15 ft., 1 target. Hit: 17 (2d12 + 4) piercing damage. 

Claws Attack. Melee Weapon Attack: +8 to hit, range 10 ft., 1 target. Hit: 13 (2d8 + 4) slashing damage damage.

Tail Attack. Melee Weapon Attack: +8 to hit, reach 15 ft., 1 target. Hit: 15 (2d10 + 4) piercing damage. Infernal Wound. Target hit by the Tail Attack must make a CON Save or receive an Infernal Wound which deals 9 (2d8) necrotic damage/round until they complete the save at the end of their turn or receive magical healing.

Fireball. Ranged Weapon Attack: DEX Save for half damage, reach 120 ft., 10 ft. radius sphere, targeting a point he can see. Hit: 28 (8d6) fire damage. 

Fire Breath (Recharge 5-6). Ranged Weapon Attack: DEX Save for half damage, 20 ft. cone, range self. Hit: 28 (8d6) fire damage.