How Nightmare's back was made

The base of the back is moreorless a strapped-on turtleshell-like cushion attached over my shoulders, around my neck and belted across my stomach with velcro-strapping - all which is eventually hidden underneath the breastplate. This is one of the very first pieces I put on when getting into Nightmare. (It's vaguely like how Saeru's wing harnesses operate with multiple areas of support, although mush more lightweight since it doesn't need to hold up anything.) The base back "pack" is simply constructed with thick felt, and it is stuffed with an interior of batting to simulate bulkier shoulder blades.

Then, I paper-mached directly onto and over that first fabric layer. What you end up with is a hard, lightweight and textured clump that you can still cut up or add on to adjust the shape. You don't even need the fabric underneath for stability (Nightmare's shoulder, mutated arm and the majority of Soul Edge are just paper and glue alone) but I just wanted something a bit softer as a base since it would be pressed up against my actual back. In this case, I used a dark blue crepe paper to give a nice "under-painting"-like depth so it didn't turn out flat and cheesy-looking when I painted it.

(These shots are actually from a different smaller-sized project, but this is an example of what paper-mache looks like when it's drying. With the above, I used the heat gun to cause the glue to dry and contract at different rates making more blobs and craters. In the case of Nightmare's back, I let the crepe paper dry on its own, which gave a much more lined sinew-y look.)

As far as the skeletal portion goes, I had the unfair advantage of working at a weird shop that sells all bits of surplus items that were designed for other purposes: thus the spine is actually made out of many tiny resin kneecaps that were originally meant to be installed into miniature skeleton models...we think. (The really nice thing in this case was that the little bones were already jointed, so my tail even swings realistically.) If I hadn't come across this totally random perfect find, I suppose I would have had to locate some plastic Halloween bone decorations to modify or even cast a completely original spine. But this saved me some time, and the mini-kneecaps were overlapped spine-like and attached to each other via epoxy to the now-dried paper-covered back. Once they were on, I used hot glue as a texture over everything, adding extra muscles and veins, and then hand-painted it all.