Hexhaven Dueling Arena is a uncommon Land card from Reality Fracture (FRA), collector number 181. Current market price: $0.20 (foil $0.31), TCGplayer market prices via Scryfall.
{T}: Add {C}. {2}, {T}: Target creature that attacked this turn becomes prepared. Activate only as a sorcery. (Only creatures with prepare spells can become prepared.) {4}, {T}: Target creature becomes prepared.