:::I guess that the most confusing part is about Al Azif. It's just that Necronomicon is sentient in Demonbane and it appear as a girl instead of a book. For the rest, Arkham City and Nyarlathotep pretty much come straight from Mythos. Finally, Demonbane's weapons are referrence to various elements. Cthugha and Ithaqua are two Great Old One created by August Derleth. Shining Trapezohedron is an artifact appear in The Haunter of the Dark, said to be a window on all space and time.