Barm

Water Form. The Barm can enter a hostile creature's space and stop there. It can move through a space as narrow as 1 inch wide without squeezing.

Freeze. If the Barm takes cold damage, it partially freezes; its speed is reduced by 20 feet until the end of its next turn.

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

Poisonous Body. Whenever the Barm is hit or missed by a melee attack, the attacker must make a DC 15 dexterity saving throw or take 10 (2d10) poison damage.

Multiattack. The Barm makes two slam attacks and a tentacle attack.

Slam. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 13 (2d8 + 4) bludgeoning damage.

Tentacle. Melee Weapon Attack: +6 to hit, reach 10 ft., 1 target. Hit: 6 (1d6 + 3) bludgeoning damage and 20 (4d10) poison damage. The target is grappled and must then make a DC 15 constitution save or be paralyzed for 1 minute. It may repeat the saving throw at the end of each of its turns.

Whelm (Recharge 4–6). Each creature in the Barm's space must make a DC 15 Strength saving throw. On a failure, a target takes 13 (2d8 + 4) bludgeoning damage. If it is Large or smaller, it is also grappled (escape DC 14). Until this grapple ends, the target is restrained and unable to breathe unless it can breathe water. If the saving throw is successful, the target is pushed out of the elemental's space.

The barm can grapple one Large creature or up to two Medium or smaller creatures at one time. At the start of each of the elemental's turns, each target grappled by it takes 13 (2d8 + 4) bludgeoning damage. A creature within 5 feet of the elemental can pull a creature or object out of it by taking an action to make a DC 14 Strength and succeeding.

Liquid Body. When the Barm would take damage from a weapon attack, it can use its reaction to contort its form and avoid damage altogether, reducing damage from the triggering attack to 0.