Hm, looks like i can't find anything by myself. I can't find access to the Mekrath's lab (or whatever it is) to rescue Haer'Dalis. It says that it is in the sewer (which is in the temple district, right?), but there is only one way to the old tunnel, where i completed the eyeless cult quest. Now, where is this Mekrath? I'm in chapter 2.

It is a secret door right beside the way to the old tunnel. Let a thief detect traps and the door turns pink.

A more descriptive direction is just down from the corner where you meet the Sewer Gang but just before the grob of goblins :D If you have an elf or a theif detecting traps it shouldnt take long to find the door at all.... there are two secret doors in that corner, one on the horizontal shaft one on the vertical... the vertical one (the one that isnt locked beyond unpicking) is the one that mekraths lair is behind :D