Marilith

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

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.

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

The marilith makes six Pact Blade attacks and uses Constrict.

Melee Weapon Attack: +10 to hit, reach 5 ft.. Hit: 10 (1d10 + 5) slashing plus 7 (2d6) necrotic damage.

Strength Saving Throw: DC 17, one Large 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.

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

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.