Wondrous Item, rare
A simple bone disc inscribed with the triangular symbol of the elemental plane. Strung with a leather cord.
The bone amulet allows the wearer expend its single charge to cast any spell they already know at its base level ( I.e. magic missile at level 1) regardless of its level. The spell still requires all prescribed components, rituals, and concentration.
The single charge is restored at dawn.
Attempting to over power a spell ( I.e. trying to cast magic missile at level 2) will cause the amulet to break beyond repair. The attempted spell will fail.