Bubbles The Dragonling

Pet - (You may begin the game with this card in
exile. You cannot begin the game with more than 1
card with Pet exiled. If this card would be exiled
while a card you own with Pet is already exiled,
put this card in your graveyard instead.)
Flying, prowess
At the beginning of your upkeep, if Bubbles is
exiled, you may roll a D20. If the result is 12 or higher, instants and sorceries you cast cost {1} less to cast until end of turn.