Mercala's Wand of Fireballs

(Requires Attunement)
This wand has 3 charges. You can use an action
to expend 1 or more charges to cast fireball
(save DC 15). For 1 charge, you cast the 3rd-level version of the spell. You can increase the spell slot level by one for each additional charge you
expend.
The wand regains 1d4 + 1 expended charges daily
at dawn. If you expend the wand's last charge, roll
a d20. On a 1, the wand crumbles into ashes and
is destroyed.