Sir,
Earlier this dark, I stumbled across a zombie standing near the stairs to Lower. Oddly enough, it was capable of speech and was repeating similar statements about its wish to stand guard on the wall once more and to be of service to Sanctuary. After a few moments, it vanished.
There can be no effect without cause, and it's reasonable to believe that a necromancer is at work, either in the Mausoleum or elsewhere in the Dunwarren ruins.
Sincerely,
Lucius Foxmantle Crone, Room Two