Cheapest priced copy (The Brothers' War): $0.99 at Card Kingdom, near mint, their price list as of .
Urza's Sylex 
Legendary Artifact · Mythic · The Brothers' War · #40
{2}{W}{W}, {T}, Exile Urza's Sylex: Each player chooses six lands they control. Destroy all other permanents. Activate only as a sorcery.
When Urza's Sylex is put into exile from the battlefield, you may pay {2}. If you do, search your library for a planeswalker card, reveal it, put it into your hand, then shuffle.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
4 printings · $0.99 to $2.29 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| The Brothers' War | 40 | Mythic | $0.99 | $0.99 |
| The Brothers' War | 312 | Mythic | $1.29 | $1.49 |
| The Brothers' War Promos | 40p | Mythic | $0.99 | $0.99 |
| The Brothers' War Promos | 40s | Mythic | — | $2.29 |
One ruling from Wizards of the Coast
- 14 October 2022The triggered ability of Urza's Sylex will resolve before the activated ability. This means that you choose whether to pay {2} and search your library before any player chooses lands. Notably, this means that the other players will get to know which planeswalker card you searched for before choosing any lands.