Sakashima the Impostor is a rare Legendary Creature — Human Rogue card from Secret Lair Drop (SLD), collector number 2784. Current market price: $20.48 (foil $13.93), TCGplayer market prices via Scryfall.
You may have Sakashima the Impostor enter as a copy of any creature on the battlefield, except its name is Sakashima the Impostor, it's legendary in addition to its other types, and it has "{2}{U}{U}: Return Sakashima the Impostor to its owner's hand at the beginning of the next end step."