Cheapest priced copy (The Brothers' War Retro Artifacts): $0.49 at Card Kingdom, near mint, their price list as of .
Key to the City 
Artifact · Rare · The Brothers' War Retro Artifacts · #27
{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.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
8 printings · $0.49 to $2.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| The Brothers' War Retro Artifacts | 27 | Rare | $0.49 | $2.99 |
| The Brothers' War Retro Artifacts | 90 | Rare | $1.29 | $2.99 |
| The Brothers' War Retro Artifacts | 90z | Rare | — | — |
| Commander 2019 | 216 | Rare | $0.49 | — |
| Commander 2021 | 248 | Rare | $0.49 | — |
| Final Fantasy Commander | 348 | Rare | $0.49 | $0.49 |
| Kaladesh | 220 | Rare | $0.59 | $1.49 |
| Kaladesh Promos | 220s | Rare | — | $2.79 |
4 rulings from Wizards of the Coast
- 20 September 2016Key to the City's last ability triggers during your untap step, but it's put onto the stack at the same time as abilities that trigger at the beginning of your upkeep step. Even though Key to the City's ability triggered first, you may order it before or after other abilities you control that are put onto the stack at this time.
- 20 September 2016Activating Key to the City's ability targeting a creature that has already been blocked won't cause it to become unblocked.
- 20 September 2016You can pay {2} only once each time Key to the City's triggered ability resolves. You can't pay more to draw additional cards.
- 20 September 2016You can activate Key to the City's first ability without targeting any creature.