Colossal Grave-Reaver is a rare Creature — Dragon card from Tarkir: Dragonstorm Commander (TDC), collector number 50. Current market price: $11.70, TCGplayer market prices via Scryfall.
Flying Whenever this creature enters or attacks, mill three cards. Whenever one or more creature cards are put into your graveyard from your library, put one of them onto the battlefield.