Cheapest priced copy (Dominaria): $2.79 at Card Kingdom, near mint, their price list as of .
Karn's Temporal Sundering 
Legendary Sorcery · Rare · Dominaria · #55
(You may cast a legendary sorcery only if you control a legendary creature or planeswalker.)
Target player takes an extra turn after this one. Return up to one target nonland permanent to its owner's hand. Exile Karn's Temporal Sundering.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
2 printings · $2.79 to $7.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Dominaria | 55 | Rare | $2.79 | $5.99 |
| Dominaria Promos | 55s | Rare | — | $7.99 |
3 rulings from Wizards of the Coast
- 27 April 2018You can’t cast a legendary sorcery unless you control a legendary creature or a legendary planeswalker. Once you begin to cast a legendary sorcery, losing control of your legendary creatures and planeswalkers won’t affect that spell.
- 27 April 2018If the target player or target nonland permanent is an illegal target as Karn’s Temporal Sundering resolves, the other target is affected as normal and Karn’s Temporal Sundering is exiled. If both targets are illegal, Karn’s Temporal Sundering doesn’t resolve and isn’t exiled.
- 27 April 2018Other than the casting restriction, the legendary supertype on a sorcery carries no additional rules. You may cast any number of legendary sorceries in a turn, and your deck may contain any number of legendary cards (but no more than four of any with the same name).