Sorceress Sellen
Waypoint Ruins (Limgrave)
Glintstone Kris, Eccentric Set
Lusat & Azur
Sorceress Sellen is the most powerful glintstone sorceress in the Lands Between, exiled from Raya Lucaria for her controversial research. Her questline involves finding her two long-lost masters and ultimately choosing between her vision for the academy's future and the established order. She is also a valuable spell vendor early in the game.
Find Sellen in the cellar. Become her student. Buy spells from her.
Located in Sellia Hideaway (Caelid), behind a hidden wall near Sellia Town of Sorcery. Complete the torch puzzle to lower barriers.
Located at Hermit Village (Mt. Gelmir), sitting near a cliff. Exhaust dialogue to receive Azur's Glintstone Crown.
Tell her about both masters. She reveals her plans and her true body location.
Find Sellen's real body chained. Destroy it.
After defeating Rennala, CHOICE: Help Sellen (gold sign) or help Jerren (red sign). Both give different rewards.
Finding both masters is required — Lusat's location is extremely hidden behind Sellia torch puzzle. Help Sellen for Glintstone Kris (best dagger for mages) and Eccentric Set. If you want her spells, buy ALL of them BEFORE finishing the quest, as she stops being a vendor afterward.
Pro Tip
Help Sellen for Glintstone Kris (best dagger for mages) and Eccentric Set. She is a vendor — buy all her spells BEFORE finishing the quest. If you help Jerren instead, you get Jerren's armor and can still buy Sellen's spells from her bell bearing, but you lose the Kris.
Sellen's quest involves a critical choice at the end: side with Sellen or Jerren. Siding with Sellen gives the Glintstone Kris (a fast-casting dagger with a projectile weapon art) and access to all sorcery vendors in her new body at the Raya Lucaria Grand Library. Siding with Jerren gives the Eccentric's Armor Set but locks you out of Sellen's later rewards and kills her permanently. The Glintstone Kris is generally considered more valuable, especially for intelligence builds. Fextralife's Sellen page has a detailed breakdown of both outcomes.
Sellen appears in three locations during her quest: Waypoint Ruins in Limgrave (first meeting, teaches basic sorceries), Sellia Hideaway in Caelid (body transfer location near Master Lusat), and Raya Lucaria Grand Library (final form if you side with her). Each location offers different sorceries for sale — her library form has the most extensive stock including high-level Glintstone sorceries. Wikipedia's Elden Ring article explains the lore connection between Sellen, Lusat, and the primeval current that drives their pursuit of forbidden sorcery knowledge.