Actions

Multiattack. The mist hulk makes two Slam attacks.
  Slam. Melee Weapon Attack: +8 to hit, reach 2 sq., one target. Hit: 16 ( 2d10+5 ) cold damage.
  Hideous Wailing (Recharge 1d6>=5 ). The mist hulk releases a wail infused with magical anguish. Each creature within 6 square of it must make a DC 14 Wisdom saving throw. A creature in the mist hulk's space has disadvantage on the saving throw. On a failed save, a creature takes 14 ( 4d6 ) psychic damage and has the incapacitated condition for 1 minute. The affected creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.