Mind's Dilation (EMN) from Eldritch Moon, available at 401 Games Canada.

• Rarity: Mythic Rare
• Finish: Normal
• Artist: Iain McCaig
• Card Text:
  Whenever an opponent casts his or her first spell each turn, that player exiles the top card of his or her library. If it's a nonland card, you may cast it without paying its mana cost.