I'm in the stout mines and I'm tired of riding those damned elevators around. I read somewhere that he was in here -- and I read that killing him for the Scanthil quest made your rogue eligible for Assassin.

Anybody seen the chump down there please?

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He is at the bottom. You need to take the right hand car (the one you fixed) and go right and right again at the junctions. You switch the junctions using the two places where you can see the tracks thru the window and there is a switch. Its a bit complex and drives you nuts, but the reward will be one of your characters can achieve Assassin, so worth the effort.