Voidpool

Amorphous. The voidpool can move through a space as narrow as 1 inch wide without squeezing.

Grappler. The voidpool has advantage on attack rolls against any creature grappled by it.

Planar Portal. The voidpool has a portal to the Void at its core. A creature that starts its turn grappled by the voidpool must make a DC 13 Strength saving throw. On a success, the creature takes 7 (2d6) force damage but isn't pulled toward the portal. On a failure, the creature takes no damage but is pulled closer to the portal. A creature that fails three saving throws before escaping the grapple enters the portal and is transported to the Void. This transportation works like the banishing an unwilling creature aspect of the plane shift spell.

Spider Climb. The voidpool can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.

Multiattack. The voidpool makes two pseudopod attacks.

Pseudopod. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 5 (1d6 + 2) bludgeoning damage plus 7 (2d6) necrotic damage. The target is grappled (escape DC 13) if it is a Medium or smaller creature and the voidpool doesn't have two other creatures grappled. Until this grapple ends, the target is restrained, and it risks being pulled into the Void (see the Planar Portal trait).