Cheapest priced copy (Phyrexia: All Will Be One): $11.99 at Card Kingdom, near mint, their price list as of .
Sword of Forge and Frontier 
Artifact — Equipment · Mythic · Phyrexia: All Will Be One · #244
Equipped creature gets +2/+2 and has protection from red and from green.
Whenever equipped creature deals combat damage to a player, exile the top two cards of your library. You may play those cards this turn. You may play an additional land this turn.
Equip {2}
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
6 printings · $11.99 to $37.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Phyrexia: All Will Be One | 244 | Mythic | $11.99 | $12.99 |
| Phyrexia: All Will Be One | 359 | Mythic | — | $37.99 |
| Phyrexia: All Will Be One Promos | 244p | Mythic | $11.99 | $17.99 |
| Phyrexia: All Will Be One Promos | 244s | Mythic | — | $20.99 |
| Spotlight Series | 3 | Mythic | $27.99 | $27.99 |
| Secret Lair Drop (Galaxy Sword) | 2817 | Mythic | $14.99 | $14.99 |
3 rulings from Wizards of the Coast
- 4 February 2023If the equipped creature somehow deals combat damage to a player on an opponent's turn, the second ability will trigger. You'll be able to cast cards you exile if timing rules allow (so, instants, mostly), but you won't be able to play a land that turn.
- 4 February 2023You must follow all normal timing rules for a card you play using Sword of Forge and Frontier's second ability and, if it's a spell, you must pay its costs to cast it.
- 4 February 2023The effect that allows you to play an additional land that turn is cumulative with other effects that do so, including itself. If the second ability triggers multiple times in the same turn, perhaps because there were multiple combats, you will be able to play that many additional lands.