Empowered Remnants can be obtained my melting down unique weapons in a furnace. The weapon is destroyed and a small portion of its power will remain in the form of an Empowered Remnant.
When this item is combined in a smithing table with a catalyst, such as a Runic Tablet or a Netherite Ingot, a gem can be formed. These gems can be then be socketed into matching sockets on unique weapons, allowing you to empower them in various ways.