Evolving Door is a rare Artifact card from Streets of New Capenna (SNC), collector number 144. Current market price: $0.40 (foil $0.38), TCGplayer market prices via Scryfall.
{1}, {T}, Sacrifice a creature: Count the colors of the sacrificed creature, then search your library for a creature card that's exactly that many colors plus one. Exile that card, then shuffle. You may cast the exiled card. Activate only as a sorcery.