Bottomless Bag of Bearings

As an action, you can spill the 1000 tiny
metal balls from their pouch to cover a level,
square area that is 10 feet on a side. A creature moving across the covered area
must succeed on a DC 10 Dexterity saving throw or fall prone. A creature moving through the area at half speed doesn't need
to make the save. The Magical Pouch refills
each day at dawn.