Lu tries out one door, doesn't hear anything, slides it open, and sees an empty bedroom. He continues this for a second door, and finds a crammed storage room. By this time, the entire party has made it's way upstairs. The third door, Lu open to find a librarry, and an unconscious man in the corner on the ground with bruises and open cuts visible.
I will go ahead and DMPC Vincenzo, as you may well need him for this battle. This is going to be a fun one.
Not seeing any danger, Fulgrim moves forward to aid the unconscious man. He lets out a sharp yell of pain as a tiny stinger suddenly sinks into his cheek, and an imp (yes, you do know it's an imp, and what imps are generally capable of; with two summoners in the party, it would be silly for you not to) appears in front of him.