http://www.youtube.com/user/IP1STOLPETE

A mini Walkthrough on how to complete Solaire's Quest Line, Saving Solaire In Lost Izalith, And Summoning Him At Lord Gwyn final boss fight. A Walkthrough done with commentary, I hope its explained and detailed enough for you, Will try and answer any of your questions the best way i can.

Save Solaire without the Chaos Servant Covenant http://www.youtube.com/watch?annotation_id=annotation_792769&feature=iv&src_vid=s5uyYe_mE4c&v=PPRduuOebb0

#1: You'll first encounter Solaire in the Undead Burg. He is in the area at the opposite end of the bridge on which the Hellkite Dragon is perched.
#2: After speaking to him in the Undead Burg, you'll next be able to encounter him in Anor Londo. You'll find him next to the first bonfire after the two Silver Knight archers.
#3: . After leaving Anor Londo, go to the Sunlight Altar in Undead Parish, and speak with him there. The Sunlight Altar is located to the right of the bonfire in the Undead Parish, right below the Hellkite Dragon's perch.
#4: Become a Chaos Servant +2 by giving 30 Humanity to The Fair Lady
#5: After killing Centipede Demon, go back and head to the Chaos Servant shortcut instead.
#6: You will noticed several Chaos Bugs in the shortcut area. There nine of them: eight normal, respawning ones; and one with glowing red-eyes. The red-eyed bug will drop a Sunlight Maggot when killed, and will not respawn; you need to kill this one to prevent Solaire from getting insane. If you return to the shortcut door after reaching Lost Izalith, Solaire will be waiting on the ground outside the door. He will be depressed over his quest for his "sun". Speaking with him here will allow you to summon him to help you during the final boss fight with Gwyn, Lord of Cinder.