Cheapest priced copy (Iconic Masters): $0.35 at Card Kingdom, near mint, their price list as of .
Trepanation Blade 
Artifact — Equipment · Uncommon · Innistrad · #235
Whenever equipped creature attacks, defending player reveals cards from the top of their library until they reveal a land card. The creature gets +1/+0 until end of turn for each card revealed this way. That player puts the revealed cards into their graveyard.
Equip {2}
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
3 printings · $0.35 to $0.79 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Iconic Masters | 231 | Uncommon | $0.35 | $0.79 |
| Innistrad | 235 | Uncommon | $0.39 | $0.79 |
| The List | IMA-231 | Uncommon | $0.35 | — |
2 rulings from Wizards of the Coast
- 17 November 2017If the equipped creature is attacking a planeswalker, the controller of the planeswalker is the defending player.
- 17 November 2017The land card is counted when calculating the bonus, and it will be put into the graveyard with the other revealed cards.