[Radek]

There are two locked doors in the Sewers.
1. The first one is near the bandits that wanted money for pass. The key in in another dungeon - in Windspear Hills.
2. The second one is on the lower floor near the "gas chamber". The key is given by Gaal whom you meet behind the "gas chamber". BEWARE! You MUST NOT kill Gaal now! Well, if you kill Gaal now then he drops some key but that key does not open the door. I don't know what does that key open. Indstead of killing Gaal, talk with him and get the key by pretending that you are a new follower of the Unseeing Eye cult. You can kill Gaal later.