The Sisters was inspired a lot by my own filthy love of 80s horror flicks, particularly Fright Night, a mutual enjoyment by the artist and I for the Dresden Files audiobooks, and my reluctance as a GM to run the wider World of Darkness games because Core/Innocents with a later dash of Hunter gets across a much better grittier horror feeling. Also probably some shenanigans in there of the many times I had to prevent my artist from playing a spellcaster in a game because he'd abuse the gonzo-bassackward powers they often get; so that's where the whole "boring powers, creative applications" mantra I tout comes from. Shows like Paranormal Witness, A Haunting, and the works of John A. Keel were pretty open influences.
Then the historical research aspect of it helped flesh it out. Cropsey, the Satanic Panic as a time period, and how those things mesh against modern paranoias and how really vapid and vulgar millennials from urban New England can be. Chuck in a healthy dose of my own personal aspects and my family life being in a huge family of vulgar, unpleasant, secret-keeping d-bags and you've sort of got the basic bog iron of the project.
Took a helluva long time to hammer that into something I enjoy showing people. Less horror, more domestic corruption, but that's street level urban fantasy for ya.