Monsters

Mariliths speak Abyssal, Celestial, and Draconic.

Combat

Spell-Like Abilities: At will-animate dead, bestow curse, chaos hammer, cloudkill, comprehend languages, darkness, desecrate, detect good, detect law, detect magic, inflict serious wounds, magic circle against good (self only), magic weapon, project image, polymorph self, pyrotechnics, see invisibility, shatter, telekinesis, teleport without error (self plus 50 pounds of objects only), unholy aura, and unholy blight. These abilities are as the spells cast by a 13th-level sorcerer (save DC 13 + spell level).

Improved Grab (Ex): To use this ability, the marilith must hit a Medium-size or smaller opponent with its tail slam attack. If it succeeds, it can constrict.

Constrict (Ex): A marilith deals 4d6+7 points of damage with a successful grapple check against Medium-size or smaller creatures. The constricted creature must succeed at a Fortitude save (DC 19) or lose consciousness for at long as it remains in the coils and for 2d4 rounds thereafter.

Summon Tanar'ri (Sp): Once per day a marilith can attempt to summon 4d10 dretches, 1d4 hezrou, or one nalfeshnee with a 50% chance of success, or one glabrezu or another marilith with a 20% chance of success. This is much as though casting a summon monster spell. Summoned creatures automatically return whence they came after 1 hour. A tanar'ri that has just been summoned cannot use its own summon ability for 1 hour.

Immunities (Ex): Mariliths are immune to poison and electricity.

Resistances (Ex): Mariliths have cold, fire, and acid resistance 20.

Telepathy (Su): Mariliths can communicate telepathically with any creature within 100 feet that has a language.

Skills: Mariliths receive a +8 racial bonus to Listen and Spot checks.

Feats: A marilith receives the Multidexteriry and Multiweapon Fighting feats as bonus feats. In combination with its natural abilities, these feats allow the marilith to attack with all its arms at no penalty.