The ape throws a rock at a 15-foot square within 100 feet that it can see. Any creatures in the target squares must make a DC 23 Dexterity saving throw. A creature takes 21 (6d6) bludgeoning damage, and if Huge are smaller are also knocked prone. A successful save halves damage and avoids being knocked prone. If the attack misses, the rock lands 1d6 squares away in a random direction. Wherever the rock lands, the area of effect becomes difficult terrain.