Cheapest priced copy (Oath of the Gatewatch): $0.49 at Card Kingdom, near mint, their price list as of .
Captain's Claws 
Artifact — Equipment · Rare · Oath of the Gatewatch · #162
Equipped creature gets +1/+0.
Whenever equipped creature attacks, create a 1/1 white Kor Ally creature token that's tapped and attacking.
Equip {1}
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
3 printings · $0.49 to $2.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Oath of the Gatewatch | 162 | Rare | $0.49 | $1.49 |
| Oath of the Gatewatch | 162† | Rare | — | — |
| Oath of the Gatewatch Promos | 162s | Rare | — | $2.99 |
2 rulings from Wizards of the Coast
- 22 January 2016You choose which opponent or planeswalker controlled by an opponent the token is attacking as it enters the battlefield. It doesn’t have to be the same opponent or planeswalker that the equipped creature is attacking.
- 22 January 2016The token is never declared as an attacking creature. It simply enters the battlefield attacking. This won’t cause any abilities that trigger “whenever a creature attacks” to trigger.