Well, they're sites from-or drawing from-Lovecraft's "Dreamlands" cycle, so they're meant to be accessible specifically through high-end astral magic. They don't so much exist apart from one another, as they are a group of inter-connected sites, existing as a set.
They're almost meant to be a sort of "Easter Egg"...remnants, ruins, and traces of a lost and shattered dimension.
Think of them as 1 site, in 5 parts
I might even add a few more "parts" in the future-quite possibly with handmade units-as there's a huge source for site material originating from the 'Dreamlands'. They'll all be hard to access rare or unique sites, though.