Actions

Multiattack The gem hurler makes two Slam attacks.
Slam Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 2d8+6 bludgeoning damage plus 1d6 piercing damage, and if the target is Medium or smaller, it must succeed on a DC 16 Strength saving throw or be pushed 5 ft. away and knocked prone.
Crystal Roll The gem hurler makes a ball of itself and rolls for 60 ft. in a 5ft. wide line. Each creature in this line must succeed on a DC 16 Dexterity saving throw or take 5d8+6 piercing damage and be knocked prone.