Antler of the green woods

This antler has markings into it, when viewed in sunlight they appear to emit a green glow. This 10-inch antler allows you to use a club or quarterstaff as a spellcasting focus for your spells. For this property to work, you must attach the antler to the weapon by pressing the antler against it for at least 10 minutes.

 It has 6 charges. While holding it, you can use a bonus action to expend 1 charge to cast the Shillelagh spell with it requiring no material components

The staff regains 1d4 + 2 expended charges daily at dawn. If you expend the last charge, roll a d20. On a 1, the staff breaks in a burst of green light and is lost forever.