The Inside the Planar Sphere side quest is associated the companion quest The Hunt for Valygar Corthala, and cannot be started unless the party either includes Valygar Corthala as a party member or has Valygar's Body in inventory. After claiming the Lavok's Sphere, the Mage Stronghold is open for Mages and Sorcerers with no other strongholds in Shadows of Amn campaign.