Helm: Lusat's Glintstone Crown

Armour: Lusat's Robe

Gauntlet: Lusat's Manchettes

Leggings: Old Sorcerer's Legwraps

Where To Find: 

(Click the link above to view the equipment and watch the getting video.)

After completing Sorceress Sellen's questline and choosing to side with Sellen, returning to Master Lusat's location in the Sellia Hideaway will reveal the entire set on the ground where he previously resided.