Question: how to summon eygon for crystal sage?
Answer: White summon sign before the Crystal Sage fight, provided the player has spoken to Irina of Carim at Firelink Shrine at least once. White summon sign in the chapel near the Dragonslayer Armour fight, if Irina has not been corrupted or killed. Sitting on a set of stairs near the bonfire, some time after saving Irina.