Cheapest priced copy (Mystery Booster 2): $4.49 at Card Kingdom, near mint, their price list as of .
Karn, the Great Creator 
Legendary Planeswalker — Karn · Rare · War of the Spark · #1
Activated abilities of artifacts your opponents control can't be activated.
+1: Until your next turn, up to one target noncreature artifact becomes an artifact creature with power and toughness each equal to its mana value.
−2: You may reveal an artifact card you own from outside the game or choose a face-up artifact card you own in exile. Put that card into your hand.
Legal inCommanderModernLegacy
Restricted inVintage
Banned inPioneer
Not legal inBrawlStandardPauper
10 printings · $4.49 to $199.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Bloomburrow Commander | 73 | Mythic | $8.99 | $17.99 |
| Mystery Booster 2 | 3 | Rare | $4.49 | — |
| War of the Spark Promos | 1p | Rare | $5.99 | $15.99 |
| War of the Spark Promos | 1s | Rare | — | $13.99 |
| War of the Spark Promos | 1s★ | Rare | — | $199.99 |
| Ravnica Remastered | 1 | Mythic | $5.99 | $6.99 |
| Secret Lair Drop | 253 | Rare | $13.99 | — |
| Secret Lair Drop | 501 | Rare | — | $9.99 |
| War of the Spark | 1 | Rare | $4.49 | $14.99 |
| War of the Spark | 1★ | Rare | $6.99 | $139.99Out of stock |
6 rulings from Wizards of the Coast
- 3 May 2019A noncreature permanent that turns into a creature can attack, and its {T} abilities can be activated, only if its controller has continuously controlled that permanent since the beginning of their most recent turn. It doesn't matter how long the permanent has been a creature.
- 3 May 2019If a permanent has {X} in its mana cost, X is considered to be 0.
- 3 May 2019Karn's last ability can't get a face-down card in exile, even if you know it's an artifact card.
- 3 May 2019In a casual game, a card you choose from outside the game comes from your personal collection. In a tournament event, a card you choose from outside the game must come from your sideboard. You may look at your sideboard at any time.
- 3 May 2019Karn's first ability affects only artifacts on the battlefield. Activated abilities that work in other zones can still be activated.
- 3 May 2019Activated abilities contain a colon. They're generally written "[Cost]: [Effect]." Some keyword abilities are activated abilities and will have colons in their reminder text, such as equip. Triggered abilities (starting with "when," "whenever," or "at") are unaffected by Karn.