Inventors' Fair is a rare Legendary Land card from Secret Lair Drop (SLD), collector number 1735. Current market price: $22.29, TCGplayer market prices via Scryfall.
At the beginning of your upkeep, if you control three or more artifacts, you gain 1 life. {T}: Add {C}. {4}, {T}, Sacrifice Inventors' Fair: Search your library for an artifact card, reveal it, put it into your hand, then shuffle. Activate only if you control three or more artifacts.