The King's Cup

Add a Shot (At the beginning of your end step, you may add shot counters to The King's Cup equal to the number of lands under your control left untapped)

{3}, {t}, Remove all shot counters from
The King's Cup. Add {x} colorless mana to your
mana pool where {x} is the number of shot
counters removed. All spells in your hand gain
Flash until the end of turn.