Cynod's Decadence

Whenever Cynod's Decadence enters the battlefield, each player exiles the top 7 cards of their library. For the rest of the game, play a subgame simulaneously, with the same starting life total and using the same libraries, graveyards, and exile zones. Put the exiled cards in each player's second hand. You go first.
Whenever you win one game, you win the other.