Is a mystery choice a spell itself or it's just an option? If yes, how much it costs. If it's a zero mana card then I could see this card as a stample in rogue. I may even considering putting this instead of fox
Oh, the Diablo 2 feeling all over again. How much is the chance that you'll get a SoJ? Also, I'd like to see the mystery choice being a card worded like "? Mana, ???" in order to become a REAL surprise (and gamble) for both you and your opponent.