Crab Swarm

Skittering, pinching crabs swarm a 10 foot square centered on a point you pick within range. The circle remains for the duration. The square is considered difficult terrain. When the square appears each creature within must make a dexterity saving throw. A creature takes 6d6 piercing damage on a failed save, or half as much damage on a successful one. A creature must also make this saving throw when it enters this spell's area for the first time on a turn or ends its turn there.