The Mimeoplasm is a mythic Legendary Creature — Ooze card from Secret Lair Drop (SLD), collector number 136. Current market price: $8.24, TCGplayer market prices via Scryfall.
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.