Stolen Identity is a rare Sorcery card from GRN Guild Kit (GK1), collector number 2. Current market price: $0.41, TCGplayer market prices via Scryfall.
Create a token that's a copy of target artifact or creature. Cipher (Then you may exile this spell card encoded on a creature you control. Whenever that creature deals combat damage to a player, its controller may cast a copy of the encoded card without paying its mana cost.)