When I was finished with the last big room where the memory crystal was, my little warning light was still yellow instead of green in one part of the room (remember that I am sworn to completely clear out every dungeon). I ran all over the place trying to figure out where the extra enemy(s) were but couldn't find them. So I finally went ahead and portaled to the Book of Liches Room, went out and finished that quest.

Then I went back in, ran down the large areas on the outside of that last section, and still couldn't find anything. Finally decided to go up the little ledge to the secret doorway and found two more eyes up there. Then found out here was a secret door behind them and a room with treasure including four books of Armageddon. I'd never known that before.