Treasure Keeper is a uncommon Artifact Creature — Construct card from Double Masters (2XM), collector number 302. Current market price: $0.20 (foil $0.16), TCGplayer market prices via Scryfall.
When this creature dies, reveal cards from the top of your library until you reveal a nonland card with mana value 3 or less. You may cast that card without paying its mana cost. Put all revealed cards not cast this way on the bottom of your library in a random order.