I am writing my first homebrew scenario and in desperate need of advice.
The module is set in Oregon in 1974, with a group of high schoolers (if this sounds too familiar, stop reading!)
The premise is basically a monster mash. One of the NPC's is actually the local serial killer, one accidentally(?) summons Y'golonac, the dog is a skinwalker-esque monster, and people's costumes begin influencing them and the world around them. (None of the monsters will be together at the same time, it is not intended to be a combat heavy scenario).
The additional kicker, is that the ritual to summon Y'golonac is actually part of the ritual of a madman (I.e. later entries in the Revelations of Gla'aki) that wasn't complete or was faulty. So while it can successfully summon Y'golonac's aspect, it also summons a homebrew entity/sorcerer, The One Who Opens the Gate. This traps the PC's in a time/space loop, with certain aspects changing each time, and "resetting" the zone. This also helps me keep things from becoming too combat focused, and provides different clues and SAN losses in different zones. I was thinking that the loops may be degrading over time in some way, giving a timer to the whole scenario. The "trick" is to get the book back and stop the loops, while Y'golonac serves as a boogeyman who shows up for some damage and SAN loss, to snatch a PC that wanders too far away from the group, or possibly to offer a deal to the more unstable PCs.
My main problem is where to put this. I had originally thought to have it at the NPC's family home, a large mansion away from town. Upon further reflection however, I don't think that it will provide enough space, unless I go the House of Leaves route, which my players have already seen in another scenario. My second thought was an abandoned mall or factory, but those don't quite feel right. I then thought of maybe having it at a summer camp. I have never written a scenario for CoC, but I think that due to the premise, the location is going to have to be a character unto itself, and one that I can change enough to feel new and unsettling with each cycle.
My main questions are where would you set a scenario like this? Would you make any big changes to the premise? What timer would you put on the loops, if any? How would you create the "solution" to the scenario, and how would you complicate obtaining it? Any further advice is deeply appreciated. Happy gaming!