This miniature magical explosive includes two tiny legs.

As an action, you may wind winder-upper's turn-key up to 10 times and set it on the ground. For each wind you give this item, it walks 1d4 feet in a straight line before exploding.  If the winder-upper encounters difficult terrain, it travels only 1 foot for each 2 feet of movement it rolled while it is in that terrain, and must roll a d4. On a roll of a 1, the winder-upper topples over upon entering the difficult terrain and explodes there.

If the winder-upper is thrown, roll a d6. On a result of a 1-4, it breaks on impact. On a 5-6, it explodes where it lands.

When the winder-upper explodes, each creature within a 20 foot radius must make a DC18 constitution saving throw or take 5d20 thunder damage, suffering half that damage on a successful save.