Staff of Frost

While holding this staff you gain _resistance_ to cold damage, and you can use an action to expend charges to cast one of the following spells, using your spell save DC: __fog cloud_ (1 charge), _ice storm_ (4 charges), _wall of ice_ (4 charges), __cone of cold_ (5 charges). The staff has 10 charges and regains 1d6+4 expended charges each dawn. When the last charge is expended, roll a d20\. On a 1, the staff melts into water and is destroyed.