[Cerek]

Personally, I would leave Improved Illyich in. Those duergar ARE annoying, but they CAN be beaten. I went through the Chateau with Tactics installed with a solo Skald myself. I admit that I wasn't able to kill ALL of the duergar I met (I had to just leave the group assembled in the tunnels next to the library, but I DID kill most of them. Then I used Yoshimo to act as a mule and carry all the booty I got off them to the Copper Coronet for me. I stored all my loot in the sewer room (where you fight the Otyugh), then loaded Yoshimo down with everything I had gathered at that point (except for items I thought I might need). Then I kicked him out of the party and told him to meet me at a local inn when we got out.

Improved Illyich was fairly tough, but I managed to defeat them with my Skald and got their magnificent bounty to use or sell.

If you need any help defeating the Chateau, just do a "Search" for "Improved Illyich". There is only a few dozen threads on the subject, so you can find lots of different tactics used by the members based on different characters and abilities.