The zeugl's lair, or nest, is the scene last "Αφεντικό" battle. It takes place in a part of the υπονόμους in the Συνοικία του Ναού which was previously inaccessible. The entrance to this area is found by going through the door immediately east of the Dwarven blacksmith shop in the nonhuman district and then descending to the cellar.
The door is locked for the duration of the game. The key to unlock it is obtained only during the Επίλογος from a wounded Order soldier lying in the street, or from Triss.