Phalanx Formation (JOU) from Journey into Nyx, available at 401 Games Canada.

• Rarity: Uncommon
• Finish: Normal
• Artist: Dan Murayama Scott
• Card Text:
  Strive — Phalanx Formation costs 1W more to cast for each target beyond the first.
  Any number of target creatures each gain double strike until end of turn. (They deal both first-strike and regular combat damage.)