The Refined Anima Core legs of Seren are part of the Anima Core of Seren set. They can be made at level 80 Crafting by combining Anima Core legs of Seren with 2 of each of the essences - Serenic, Sliskean, Zamorakian, and Zarosian - after the ability to craft Refined Anima Core of Seren armour has been unlocked by earning 2,000 Serenist reputation. Crafting them grants 500 Crafting experience.
The legs degrade back to unrefined legs after 100,000 charges of combat, where they can be crafted again using more essences. It can also be restored to 100% charge at any time using 2 of each essence (essentially re-creating them).