Flockchaser Phantom (MOC) from March of the Machine Commander, available at 401 Games Canada.

• Rarity: Rare
• Finish: Normal
• Artist: Lorenzo Mastroianni
• Card Text:
  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.)
  Flying, vigilance
  Whenever Flockchaser Phantom attacks, the next spell you cast this turn has convoke.