The Mystery Raceway is a rare Land card from Unknown Event (UNK), collector number RZ11c. Current market price: $30.00, TCGplayer market prices via Scryfall.
Start your engines! {T}: Add {C}. Max Speed — {W}{U}{B}{R}{G}, {T}: Mill seven cards. Choose a playtest card from among them. You may cast it without paying its mana cost. If Team Cloudspire won the race, copy it and you may choose new targets for the copy. If Team Speed Demons won the race, each opponent loses life equal to its mana value. The Mystery Raceway can be your commander.