I searched the entire forums about it... And the only info I could find is that after talking to the 3 ghosts (I already did), you need to kill a (spoiler) water snake in front of moathouse secret entrance (/spoiler) Well, I visited the place, tried casting spells on it and... no creature there. Seriously, this quest need some reworking and fixed, lots of people confused about it (also it is a Guide dang'it quest, who the hell will figure the swamp refers to that pond on the moathouse?), and the quest blocks resting on the castle (that I think should be a major feature of the castle), thus a broken quests, breaks the castle too.
