So while I enjoy the back story for explaining how all of the investigators gathered in Arkham this go around, I would like a little more backstory as to why 12 gates have to be closed this time- sort of a back story to the specific scenerio.
Since they gates can be closed but not sealed I imagine them as being more numberous but less stable. Perhapes whoever performed the ritual to call to Shub got interrupted by a police raid, leaving more numerous but less well "anchored" gates forming along Arkham's laylines?
Any one have a 1 or 2 paragraph story to explain this? I have my own that I am editing right now that I want to post later. I think it alway adds a little something to explain why the scenerio is set up the way it is.