Daan,
spoilers
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the fallen paladins are in the open area to the south of the building where you met Lt Aegisfield. Easiest way to get there if you come in through the north west district entrance is to head south west along the wall and go through the alley between the wall and the end of the building. However going all the way around the building and coming up from the other way gives your party more room to manoevure.
Also, if you return to the tanners' basement later in the game you might find a visitor... or two
Kez