Devouring Light (RAV) from Ravnica: City of Guilds, available at 401 Games Canada.

• Rarity: Uncommon
• Finish: Normal
• Artist: Pete Venters
• Card Text:
  Convoke (Each creature you tap while playing this spell reduces its cost by 1 or by one mana of that creature’s color.)
  Remove target attacking or blocking creature from the game.