Marilith

Large Fiend (Demon), Chaotic Evil

AC 16 Initiative +10 (20)
HP 220 (21d10 + 105)
Speed 40 ft., Climb 40 ft.

Skills Perception +8
Resistances Cold, Fire, Lightning
Immunities Poison; Poisoned
Senses Truesight 120 ft.; Passive Perception 18
Languages Abyssal; telepathy 120 ft.
CR 16 (XP 15,000; PB +5)

Traits

Demonic Restoration. If the marilith dies outside the Abyss, its body dissolves into ichor, and it gains a new body instantly, reviving with all its Hit Points somewhere in the Abyss.

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

Reactive. The marilith can take one Reaction on every turn of combat.

Actions

Multiattack. The marilith makes six Pact Blade attacks and uses Constrict.

Pact Blade. Melee Attack Roll: +10, reach 5 ft. Hit: 10 (1d10 + 5) Slashing damage plus 7 (2d6) Necrotic damage.

Constrict. Strength Saving Throw: DC 17, one Medium or smaller creature the marilith can see within 5 feet. Failure: 15 (2d10 + 4) Bludgeoning damage. The target has the Grappled condition (escape DC 14), and it has the Restrained condition until the grapple ends.

Bonus Actions

Teleport (Recharge 5–6). The marilith teleports up to 120 feet to an unoccupied space it can see.

Reactions

Parry. Trigger: The marilith is hit by a melee attack roll while holding a weapon. Response: The marilith adds 5 to its AC against that attack, possibly causing it to miss.