Staff of Spell Storing

Equipped creature has "{u}, {t}: Counter target activated mana ability. Put a charge counter on
Staff of Spell Storing."
{1}{u}{u}, {t}: Add X mana of any color to your
mana pool, where X is the number of charge
counters on Staff of Spell Storing. Then remove
all charge counters from Staff of Spell Storing.
Equip {u}