when I looked for Celtic folklore ideas, since the synopsis said that was what 'the horror in the glen' story was about, and 'incense of abomination' was about 'witchcraft'... Google translate told me that one option for witch in Irish was Sol Ban, a type of spirit worker, but another translation sight told me sol was 'solid' and ban was white in Irish. So naturally Solid White Witches that work with spirits connected with Geister Damen (ghost ladies in German) in mind.
I only had about the last 36 hours of the jam to work on it, and I used so much time figuring out the worldbuilding notes, for the Sul-bahn, the continent they come from, their beliefs system that was manipulated by the family Courbass, the trade war involved in conspiracies and trade goods and routes, and how the ghost ship 'flushing queen' got enmeshed in it. lol most of which is barely hinted at in this adventure.
I'm probably going to make it a series of materials. it's too much fun to play world builder to confine it to 8 pages of hints.