How high is your INT, WIS, and CHA? While talking to Hargrimm, you should be able to ask him why you are a prisoner and whether you can see the Silent King. It's at this point he'll tell you that you have to prove yourself trustworthy and gives you several quests to that end. There are other quests in here, too, and there's even a Merchant selling some hard-to-find items. If your CHA is high enough, you can convince Stale Mary to show you another route to the Silent King for a bunch of experience points. It's worth your while to re-load and re-do the Catacombs. You know what to expect, now. BTW, those Lesser Vargouilles and Cranium Rats are susceptible to Morte's Litany of Curses.
You have to side with the Dead Nations (the route to go for Lawful Good Alignment) or Many-As-One in the Warrens of Endless Thought, in order to reach the Drowned Nations (your ultimate destination). If you go with Many-As-One, be warned, the Cranium Rats are treacherous.
I've never had a problem leaving the Dead Nations back toward the Catacombs. Are you sure you're trying to use the right exit?
__________________
There's nothing a little poison couldn't cure... What happened here was the gradual habituation of the people, ... to receiving decisions deliberated in secret; to believing that the situation was so complicated that the government had to act on information which the people could not understand, or so dangerous that, even if he people could understand it, it could not be released because of national security. | 
I really done it this time! 
Linear Mode
