1) you can use the torch once she and her "underling" are unable to see you or dead. that will reveal the cellar door.
2) the armory is the "cell" with the purple lock in the prison (the cellar of the house where all the mountain warrior reside). I didn't find anything useful in there but maybe you have more luck.
3) If your perception is not high enough you can try to get a "burn my eyes" scroll and use that on the character with the highest perception. This should boost your perception high enough so that you can see the footprints (it did for me at least)
That's the armory? That's so disappointing. I went to the prison before I started looking for the armory and bypassed the locked gate with Phoenix Dive...
