You can check out game guide on 12SKY LAST EMBER
Enchant stone trader
You can exchange unused enchanted equipment for Tan Stones through the Trade NPC in town.
※ Only equipment with +12 enchant or higher can be exchanged for Tan Stones. ※ The number of Tan Stones obtained is not related to the grade of the equipment, and varies depending on the enchantment stage and part. ※ Equipment exchanged for Tan Stones cannot be restored, so please proceed with caution.