Not sure if possible without having all of the collectibles, but I can at least give you the information required as if you did.
In West End, beyond a quarantine barrier, you'll find another group of survivors such as the Baker brothers, Carolyn Price and her daughter Carol, but more importantly, the Primate of the Brotherhood of Saint-Paul Stole, Usher Talltree. He'll request your help in retrieving valuable information from the Guard of Priwen which will take you back into the Grand Guignol Theater (where you encountered Doris) but you can only enter here as a part of the story once more.
In the same catacomb-like entry leading to Usher are four pressure plates. The one you cross upon entering, one as you head towards Usher, and two others, forming a diamond-like display across the small room. The key to unlocking the door for the "True Dragonbane" weapon as well as getting this trophy lies in standing on these plates in a specific order. The order will be displayed as such below: NE, NW, SE, SW. When you're standing in the middle of the small room, N falls between both entry plates. So, the order is SE, NE, NW, NE, SE, SW. Make sure the plates sink completely before moving on to the next. Once the correct sequence is performed, the wall near the SE plate should shake and reveal the hidden alcove, and upon entering, the trophy and treasure is yours.
You can actually uncover all of this information provided throughout the game's collectibles. Upon returning Usher's journal to him, unread, you'll be given the designation of the four plates by their symbols, and there are six different Stole collectibles that each have a specific symbol and a number of dots associated with them.