As an action, you can spread a bag of caltrops to cover a 1 sqr. (1.5m)-square area. A Large or smaller creature entering this area must succeed on a DC 15 Dexterity save or stop moving and take 1 piercing damage. This damage reduces the creature’s walking speed by 2 sqr. (3m) until it regains at least 1 hit point. A creature moving at half speed through the area avoids the save.