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

Multiattack. Zargath's Possessed makes two melee or ranged attacks.

Elemental Rapier. Melee Weapon Attack: +13 to hit, reach 5 ft., 1 target. Hit: 14 (2d8 + 5) piercing damage. On hit, the target also takes 5 (1d10) of elemental damage depending on the roll (1-10=fire, force, lightning, acid, psychic, poison, cold, radiant, thunder, necrotic respectively).

Elemental Longbow. Ranged Weapon Attack: +13 to hit, range 150/600 ft., 1 target. Hit: 9 (1d8 + 5) piercing damage. On hit, the target also takes 5 (1d10) of elemental damage depending on the roll (1-10=fire, force, lightning, acid, psychic, poison, cold, radiant, thunder, necrotic respectively).

Counterspell. Zargath's possessed can cast counterspell at 8th level as a reaction without using a spell slot.

Zargath's Possessed can take 3 legendary actions, choosing from the options below. Only on legendary action option can be used at a time and only at the end of another creature's turn (unless stated otherwise). Zargath's Possessed regains any spent legendary actions at the start of its turn.

Detect. Zargath's Possessed makes a Wisdon (Perception) check.

Spectral Longbow. Summon a spectral longbow and make a ranged weapon attack: +13 to hit, range 120/400ft., Hit: 15 (2d10 + 4) piercing damage plus 3 (1d8) psychic damage.

Summon Demon (Costs 2 Actions). Roll 1d4 and summon 1 demon (1=shadow demon, 2=Barlgura, 3=Vrock, 4=Chasme) within 30ft. under your control and immediately takes an attack action. They are placed after Zargath's Possessed in the initiative order. Only 1 demon can be summoned and controlled by Zargath's Possessed at once through this action.

Command Minions. Command a summoned Demon to take an action against target creature.

Demon Wall. Upon being hit by another creature but before taking damage or effects, Zargath's Possessed may chose a Demon summoned by Zargath's Possessed within 20ft. of themselves and force them to take the effects of the hit instead of Zargath's Possessed.