Az'leor, The Storm Scourge

Flying
When an opponent casts an instant or sorcery
spell, exile it with a spell counter, if there isn't a
card in exile with a spell counter already.
You may cast instant and sorcery spells with
spell counters on them from exile, and spend
mana as though it's mana of any color. If you do
return it to it's owner's hand.