A caltrop is a four-pronged iron spike crafted so that one prong faces up no matter how the caltrop comes to rest. You scatter caltrops on the ground in the hope that your enemies step on them or are at least forced to slow down to avoid them.
As an action, you can spread a single bag of caltrops to cover a 5-foot-square area. Any creature that enters the area must succeed on a DC 15 Dexterity saving throw or stop moving and take 1 piercing damage. Until the creature regains at least 1 hit point, its walking speed is reduced by 10 feet. A creature moving through the area at half speed doesn't need to make the saving throw.