This quest requires a lot of exploration and interacting with 'things' (sometimes in secret areas). Without a guide, you'll probably need to fully explore the place (use scrolls of detection to make sure you've found everything). Also, one of the steps will only trigger after you have already completed another step first. Find out why The Abbot is still around and why he isn't a regular undead, did you try attacking him?. Check back with Saint's ghost whenever you think you've found
