MM page 58.
Innate Spellcasting. The glabrezu's spellcasting ability is Intelligence (spell save DC 16). The glabrezu can innately cast the following spells, requiring no material components:
Magic Resistance. The glabrezu has advantage on saving throws against spells and other magical effects.
Multiattack. The glabrezu makes four attacks: two with its pincers and two with its fists. Alternatively, it makes two attacks with its pincers and casts one spell. Pincer. Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 16 (2d10 + 5) 2d10+5 bludgeoning damage. If the target is a Medium or smaller creature, it is grappled (escape DC 15). The glabrezu has two pincers, each of which can grapple only one target. Fist. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 7 (2d4 + 2) 2d4+2 bludgeoning damage. Variant: Summon Demon (1/Day): The demon chooses what to summon and attempts a magical summoning. A glabrezu has a 30 percent chance of summoning 1d3 vrocks, 1d2 hezrous, or one glabrezu. A summoned demon appears in an unoccupied space within 60 feet of its summoner, acts as an ally of its summoner, and can't summon other demons. It remains for 1 minute, until it or its summoner dies, or until its summoner dismisses it as an action.