Incorporeal Movement. The Haunter can move through other creatures and objects as if they were difficult terrain. It takes 5 (1d10) force damage if it ends its turn inside an object.

Claw. Melee Weapon Attack: +4 to hit, reach 5 ft., 1 target. Hit: 4 (1d4 + 2) slashing damage. 

Manipulate Stone. The cavern haunter chooses once piece of stone, rock, earth, or similar marital, that is large or smaller, such as a stalactite, that is within 20 feet of it. The piece of earth moves up to 40 feet, to a location of the Cavern haunter's choice. 

If the earth hits a creature, the creature make a DC 12 strength saving throw, taking (2d8) bludgeoning damage on a failed save, or half as much on a successful one. A creature who fails the save by 5 or more is also knocked prone.