Cheapest priced copy (Darksteel): $17.99 at Card Kingdom, near mint, their price list as of .
Panoptic Mirror 
Artifact · Mythic · The Zeta Set · #110
Imprint — {X}, {T}: You may exile an instant or sorcery card with mana value X from your hand.
At the beginning of your upkeep, you may copy a card exiled with this artifact. If you do, you may cast the copy without paying its mana cost.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
4 printings · $17.99 to $79.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Darksteel | 136 | Rare | $17.99 | $79.99 |
| The Zeta Set | 110 | Mythic | — | — |
| The Zeta Set | 231 | Mythic | — | — |
| The Zeta Set | 352 | Mythic | — | — |
7 rulings from Wizards of the Coast
- 1 December 2004You may imprint a card on Panoptic Mirror in response to the upkeep-triggered ability. If you do, that card is available to copy when the triggered ability resolves.
- 1 December 2004Exiling a card when the activated ability resolves is optional. If you choose to exile a card, you can exile only a card with mana value equal to X.
- 1 December 2004As Panoptic Mirror's triggered ability resolves, it allows you to create a copy of one of the instant or sorcery cards imprinted on Panoptic Mirror in the Exile zone (that's where the imprinted card is) and then cast it without paying its mana cost.
- 1 December 2004You don't pay the spell's mana cost. If the spell has X in its mana cost, X is 0. You do pay any additional costs for that spell. You can't use any alternative costs.
- 1 December 2004The triggered ability triggers only once each upkeep, not once per imprinted card. If no cards are imprinted on Panoptic Mirror when the triggered ability resolves, it does nothing.
- 1 March 2005The creation of the copy and then the casting of the copy are both optional.
- 18 April 2017To imprint a split card, you pay X equal to card's mana value, determined by the combined mana cost of its two halves. If the copied card is a split card, you choose which one side of it to cast, but you can't cast both sides.