Large Fiend (Demon), Chaotic Evil
Armor Class 16 Initiative +10 (20) Hit Points 220 (21d10 + 105) Speed 40 ft., Climb 40 ft.
Saving Throws Str +9, Dex +5, Con +10, Int +4, Wis +8, Cha +10
Skills Perception +8
Damage Resistances Cold, Fire, Lightning
Damage Immunities Poison; Poisoned
Senses Truesight 120 ft.; Passive Perception 18
Languages Abyssal; telepathy 120 ft.
Challenge Rating 16
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 has Advantage on saving throws against spells and other magical effects.
The marilith can take one Reaction on every turn of combat.
The marilith makes six Pact Blade attacks and uses Constrict.
Melee Attack Roll: +10, reach 5 ft. Hit: 10 (1d10 + 5) Slashing damage plus 7 (2d6) Necrotic damage.
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.
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.