Slimer, Voracious Apparition - The Mimeoplasm (SLD-1773) - Secret Lair Drop / Slimer, Voracious Apparition (Borderless)

As The Mimeoplasm enters, you may exile two creature cards from graveyards. If you do, it enters as a copy of one of those cards with a number of additional +1/+1 counters on it equal to the power of the other card.