Multiattack

The mountain giant makes two slam attacks.

Slam

Melee Weapon Attack: +15 to hit, reach 20 ft., one target. Hit: 21 (2d12 + 8) bludgeoning damage.

Boulder

Ranged Weapon Attack: +15 to hit, range 100/400 ft., one target. Hit: 40 (5d12 + 8) bludgeoning damage.

Boulder Spray (Recharge 5-6)

The mountain giant unleashes a barrage of boulders in a 60-foot cone. Each creature in that area must make a DC 22 Dexterity saving throw. On a failure, a creature takes 58 (9d12) bludgeoning damage and is knocked prone and restrained. On a success, the creature takes half the damage and isn't knocked prone or restrained. A target, including the restrained creature can take an action to make a DC 20 Strength (Athletics) or Dexterity (Acrobatics) check, freeing the restrained creature on a success.