Pretty much everyone in this adventure are supporting characters created as part of the player characters' backgrounds, specifically Renraw Kem and Katadid Leach, and the adventure was their players' ideas.
Given the Gothic madness of Kem House, it's ironic that Renraw's player has resisted me characterizing his character as evil, although that may predate his ideas about Kem House.
If I'd had this setting laid out in front of me from the beginning, I think I would have done a kind of Castle Amber-style adventure set there early on. With the fugitives on the run, it's not practical at this point, especially with the Green Mountain plot line galloping along full-out.
The next Midwood campaign will likely jump forward in time, either six or 12 months. Maybe an interlude with Kem House can be worked in, or maybe it'll just be source material for a future campaign with new characters. I like to think of the house like Stephen King and Peter Straub's Black House, as a malign site independent of its residents. Exploring why and what it means for those around it would be interesting, I think. There's a lot of interesting mythic things that can be done with "the house that everyone avoids," especially if it were to retreat somewhat from town, deeper into the wild portions of the Tulgey Wood.