Pangaea666: I've only done the expansion once, so don't know how much you need to do there to get through it all. There is a chap in the slimy corridors for example, with a useful hint for later. Don't know if you have to confront him or not to progress, but worth a shot if you haven't done it yet. He's in the far west of the southern pits area.
The way I happened to do this was that I talked to the golem in the north of the big spider room. The one in the small nook in the north of the room. Have you talked to him? There are some riddles then you are sent to the riddle room IIRC.
Then there is the one in the family tomb room, but first you have to disable the trap across the room there (that you are warned about) by getting the bone wardstone and using it in the machine room. That will disable the traps. Then you can "magic-click" the bed in the family tomb room, and you are sent to the riddle golems for more questoning.
Then there is the small room with the many treasures. From there you should get sent to the riddle room as well. Use your thief's detect traps at all times, because there are quite many traps and hidden doors. For example, quite far east in the slime area there is a hidden door to some corridors. In there, you will get to a throne room, from where you are sent to the riddle room.
If I recall correctly, there are four riddle sequences (hmm, or was it three?), including the one with the golem in the north of the room where you were attacked by spiders.
Don't know if it's needed, but from time to time you can talk to the spirit where you started this level as well. This is important at the very end, when you have solved all the riddles.
i've done all the above, except the throne room which seems to be heavily bugged for me. It would lead me to the final riddle. I even tried a fresh install to a new computer but still nothing. I've completely ran out of options