W. G. Grottendieck's Stones

Origin
W. G. Grottendieck was a Dutch explorer resting on his Sumatran abode when a strange thing occurred. He woke up approximately one in the morning to find small black stones on top of him. Hot to the touch, they appeared to have fallen through the roof without leaving any holes and gently hovered down rather than falling normally.

Effects
The owner will have the stones multiply at a constant rate throughout the night. Said stones will have to disposition to materialize and fall right onto the owner’s head.