I always thought it was very funny how I could turn the defensive design of the Merc Guild building back on it's inhabitants. I found two different ways of using those archer-slot windows in the entrance foyer to kill Mercs. It seems to me that the windows were made with the lower edge a little too high. So instead of the 4 archers stationed in the hallways opening fire on me (that is my characters) as soon as I come through the front door, they can't even seem to tell that I'm there. I however can walk right up to a window, reach through, and chop them down with complete impunity.
After I had cleared out all the other wimpy thiefs and archers, I discovered a way to use the archer-windows again to deal with those "..of the Sword" knights. I would open the door leading into one of their rooms, then run back out to the central room, up the back stairway, across the mezzanine, and down into the archer-hallway.
If I had timed it right, some of the Knights would run into the foyer area and right up to the window I was standing in front of. And unlike the similar trick with the prison cell grating, this was 100% safe. The Knights were never able to attack me while I could hit them all I wanted.
It was a bit tricky getting them to run into the foyer. Some would fetch up in the little corners formed by the pillars just to the left and right of the inner door. When I was down to just one Knight left, I would switch to another tactic I discovered.
I would run back into the central room and let the knight get close enough to lead him up one of the stairs. Then I'd just run along the mezzannine and run off the end of it right at the foyer door. The Knight would be stuck up on the mezzannine where I could just pick him off with ranged fire.