Crown of Convergence is a rare Artifact card from Ravnica: City of Guilds (RAV), collector number 258. Current market price: $0.27 (foil $1.20), TCGplayer market prices via Scryfall.
Play with the top card of your library revealed. As long as the top card of your library is a creature card, creatures you control that share a color with that card get +1/+1. {G}{W}: Put the top card of your library on the bottom of your library.