Caustic Balor

Death Throes. The balor explodes when it dies. Dexterity Saving Throw: DC 20, each creature in a 30-foot Emanation originating from the balor. Failure: 31 (9d6) Acid damage plus 31 (9d6) Force damage. Success: Half damage. Failure or Success: If the balor dies outside the Abyss, it gains a new body instantly, reviving with all its Hit Points somewhere in the Abyss.

Withering Aura. At the end of each of the balor’s turns, each creature in a 5-foot Emanation originating from the balor takes 13 Necrotic damage.

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

Magic Resistance. The balor has Advantage on saving throws against spells and other magical effects.

Multiattack. The balor makes one Tongue attack and one Bite attack.

Acid Tongue. Melee Attack Roll: +14 reach 30 ft. Hit: 18 Force damage plus 17 Acid damage. If the target is a Huge or smaller creature, the balor pulls the target up to 25 feet straight toward itself, and the target has the Prone condition.

Bite. Melee Weapon Attack: +14 to hit, reach 15 ft., one target. Hit: 15 piercing damage plus 15 acid damage. 

Teleport. The balor teleports itself or a willing demon within 10 feet of itself up to 60 feet to an unoccupied space the balor can see.

Caustic Volley. The balor casts a spray of acid in a 30 foot cone. Any creature in the area must make a DC 18 Dexterity saving throw or take 4d6+6 Acid damage, or half as much on a success. 

Dissolve - Trigger: The balor is hit with a weapon attack. Action: The balor dissolves through a pool of acid, reducing the attack's damage by half. The balor can then reapear within 10 feet of its original location.