After a while, the commotion seems to quieten down somewhat. From the sounds of it, Tass suspects they are getting organised about dousing the fires. In maybe ten minutes more, he figures, the fire and his smoke screen will be dealt with.
Chancing a peek, Tass sees he has come half way around the back of the cathedral now, and that there are a couple of ruinous outbuildings just over yonder... he crawls along the drain to reach them, and then finally gets out of the muck between two half collapsed walls to have a better look around...
Tass realises he is now on the opposite side of the cathedral to the supply yard. So while most of the men are over there dealing with the fires, he should have a good chance of sneaking across to the Cathedral walls. But how to get in? The door he used last time is all the way around the front, and nearer to all the activity.