Gibbering Mouther

The ground in a 10-foot Emanation originating from the monster is Difficult Terrain.

The monster babbles incoherently while it doesn't have the Incapacitated condition. Any creature that starts its turn within 20 feet of the monster while it is babbling must succeed on a DC 10 Wisdom saving throw or roll 1d8 to determine what it does during the current turn: 1–4, the target does nothing; 5–6, the target takes no action or Bonus Action and uses all its movement to move in a random direction; 7–8, the target makes a melee attack against a randomly determined creature within its reach or does nothing if it can't make such an attack.

Melee Weapon Attack: +2 to hit, reach 5 ft., one creature. Hit: 2d6 piercing damage. If the target is a Medium or smaller creature, it has the Prone condition. The target dies if it is reduced to 0 Hit Points by this attack. Its body is then absorbed into the monster, leaving only equipment behind.

Dexterity Saving Throw: DC 10, each creature in a 10-foot-radius Sphere centered on a point within 30 feet. Failure: 2d6 radiant damage, and the target has the Blinded condition until the end of the monster's next turn.