Guilds of Ravnica

Chance for Glory | Instant | | Creatures you control gain indestructible. Take an extra turn after this one. At the beginning of that turn's end step, you lose the game. | Bram Sels

March of the Multitudes | Instant | | Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.) Create X 1/1 white Soldier creature tokens with lifelink. | Zack Stella

Mnemonic Betrayal | Sorcery | | Exile all opponents' graveyards. You may cast spells from among those cards this turn, and you may spend mana as though it were mana of any type to cast those spells. At the beginning of the next end step, if any of those cards remain exiled, return them to their owners' graveyards. Exile Mnemonic Betrayal. | Clint Cearley