Bag of Expanding rocks

A bag of 100 pebble sized rocks.

Once a rock leaves the bag after 5 seconds it will expand instantly to a 10ft by 10ft by 10ft cube. Any creature underneath must succeed a DC 25 strength save or take 10D10 impact damage, on a successful save you will have chance to throw the cube.

If the cube doesn't touch the ground for 10 seconds it will enlarge to 100ft by 100ft by 100ft and can not be moved except by telepathic means and anything caught underneath will be crushed.