Actions

Proboscis. Melee Weapon Attack: +5 to hit, reach 5 ft., one creature. Hit: 16 (4d6 + 2) piercing damage plus 24 (7d6) necrotic damage, and the target's hit point maximum is reduced by an amount equal to the necrotic damage taken. If this effect reduces a creature's hit point maximum to 0, the creature dies. This reduction to a creature's hit point maximum lasts until the creature finishes a long rest or until it is affected by a spell like greater restoration.   Variant: Summon Demon (1/Day)
The demon chooses what to summon and attempts a magical summoning. A chasme has a 30 percent chance of summoning one chasme. 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.