Illusionary Mask (LEB) from Limited Edition Beta, available at 401 Games Canada.

• Rarity: Rare
• Finish: Normal
• Artist: Amy Weber
• Card Text:
  X: You can summon a creature face down so opponent doesn’t know what it is. The X cost can be any amount of mana, even 0; it serves to hide the true casting cost of the creature, which you still have to spend. As soon as a face-down creature receives damage, deals damage, or is tapped, you must turn it face up.