Caltrops (bag of 20)

You can use an action to spread a bag of caltrops that covers a square area 5 feet on a side. Any creature that enters the area makes a DC 15 Dexterity saving throw or it stops moving this turn and takes 1d4 piercing damage. Taking this damage reduces the creature’s walking speed by 10 feet until it regains at least 1 hit point. A creature moving through the area at half speed doesn’t need to make the save.