Polymorphous Rush (JOU) from Journey into Nyx, available at 401 Games Canada.

• Rarity: Rare
• Finish: Normal
• Artist: Ryan Barger
• Card Text:
  Strive — Polymorphous Rush costs 1U more to cast for each target beyond the first.
  Choose a creature on the battlefield. Any number of target creatures you control each become a copy of that creature until end of turn.