Argopoda

Asphyxiation. If a creature ends its turn inside the gas cloud, they must make a DC 17 Constitution saving throw, or fall asleep. If the creature is already asleep, they take 1d4 poison damage. This damage can not be reduced or negated, nor does the creature wake up from it. 

Gaseous form. While in this form, the Argopoda's only method of movement is a flying speed of 10 feet. The Argopoda can enter and occupy the space of other creatures. The Argopoda has resistance to nonmagical damage, and it has advantage on Strength, Dexterity, and Constitution saving throws. The Argopoda can pass through small holes, narrow openings, and even mere cracks, though it treats liquids as though they were solid surfaces. It can’t fall and remains hovering in the air even when stunned or otherwise incapacitated. Being struck by lightning damage makes the gas cloud emit purple light while truck, and afterwards the Gaseous form ceases to be active.

Tentacles. Melee Weapon Attack: +10 to hit, reach 15 ft., one target. Hit: 20 (3d8 + 6) bludgeoning damage. If the target is a creature, it is grappled (escape DC 17). Until this grapple ends, the target is restrained, and the Argopoda can't use its tentacles on another target.

Crush. Melee Weapon Attack: +10 to hit, reach 15 ft., one target. Hit: 20 (3d8 + 6) bludgeoning damage. The Argopoda uses its tentacles on to crush the creature it has grappled. The creature grappled can make a DC 17 Strength saving throw, and on success take half damage instead.

Gas Cloud (Recharge 5-6). The Argopoda turns into an invisible gas cloud, it's Gaseous form. This gas is not visible to the eye, has no smell. Its a 15- foot-radius cloud of gas centered on the Argopoda. The Argopoda can dismiss this form as an action, and can't recharge while it's still in Gaseous form.