Ok, so I've defeated the eight chambers. Thats all well and good, I went back and told Aruma i think her name was, we went through the routine she said it was ok to enter. So, I went back down stairs and simply cant find the door to the underdark. I ended up killing the entire monastary in my rage.
Next to the steps up to the monestary from the 8 chambers there are some more steps going down, they can be tricky to spot as they caught me out the first time i played