Seems like the City of Doors needs a Jack the Ripper.
I'd think he'd end up being a Dabu in the end. He encases families in masonry after killing them, leaving choked spaces where the dead air has been left to collect.
It would be up to the players what to do once they caught him. How does one bring a Dabu to justice?
Thoughts and theories?
Well maybe he (or she) could be doing it in the Hive and part of the reason he hasn't been caught yet is two fold. 1) people in the hive often don't care if someone disapears and 2) When someone does care it gets mixed up with the Kadyx a monster that roams through the Hive and eats people sometimes and will often arrange their remains in unusal ways. Few have ever seen the monster and hangs out only in the Slags which is the worst part of the worst part of town (The hive.)
Perhaps if he expands the rumors might end up being that the Kadyx is moving outward. Then again if you want the city to be talking about and possibly caring enough to do something about it the Hive is the very worst spot to have him come from. Then again you could have him start there and then move out into better districts.
P.S. the Kadyx is from In the Cage: A guide to Sigil in the Hive Section