Antique Sword

Antique Sword can be found in the temple chests below Sage and Grit. It is obtained as a chest loot item tied to that temple area, making it a progression reward rather than something crafted or bought.

Because its source is limited to those temple chests, it is only available once you have access to the relevant temple content. If you are exploring that area, checking the chests beneath Sage and Grit is the way to obtain it.