Key to the City is a rare Artifact card from The Brothers' War Retro Artifacts (BRR), collector number 27. Current market price: $0.40 (foil $1.27), TCGplayer market prices via Scryfall.
{T}, Discard a card: Up to one target creature can't be blocked this turn. Whenever this artifact becomes untapped, you may pay {2}. If you do, draw a card.