Page 2: Buffalo Bill Transformed
Physical transformation as the result of contact with extradimensional entites is a trope of the "Cthulu Mythos" strories of H.P. Lovecraft. Bill here is not based on a particular instance from Lovecraft's stories, though the general tendency for Lovecraft's extradimensional thingies to manifest themselves in our dimension via tentacles, suckers, claws and slime has been followed.
Page 4: Cannibalism in the Old West
Possibly the most famous tale of cannibalism among the American pioneers is story of the Donner Party. In the winter of 1846-7, a party of American settlers consisting mostly of the families of George and Jacob Donner became snowbound near Alder Creek in the Sierra Nevada mountains. The episode became famous because it is thought that some members of the party resorted to eating the dead in order to survive. There is now a memorial at the site of the disaster at Alder Creek, and the surrounding area has been designated the Donner Memorial State Park.
A further source of inspiration was Antonia Bird's 1999 feature film Ravenous.
Page 5: Lovecraftian "Elder Gods"
In H.P. Lovecraft's stories, the Elder Gods (sometimes referred to as Old Ones, though his terminology does not appear to be consistent; in some tales this refers to a very specific alien race from out dimension) are extradimensional entities of unimaginable age and unguessable power.
When designing the creature, Ian asked me to base the body shape on the work of modernist sculptor Henry Moore (hence the convoluted organic form with a hole in the middle), and to make it transparent and "full of stars and galaxies" - a phrase that reminded me of the classic line uttered by astronaut Dave Bowman in Arthur C. Clarke's novel 2001 (and the 1984 film sequel 2010, though not the 1969 Stanley Kubrick film). On discovering that the second giant monolith TMA-2 is in fact a hyperspace conduit, Bowman manages to utter the words "Oh my God, it's full of stars!" before being swept off into the unknown.