Gloomy Man, Gloomy Sunday.

(Headcanon by marki-trash-blog on Tumblr)
"Dark's often in pain which is partially the reason you wouldn't see much of him. Considering he's walking around in the next closest thing to a corpse, it's no wonder. Joints become stiff, bones turn weak. No one knows how his body has lasted him for so long, it most likely has to do of course with the original demon's magic, but the poin it, he still has days where he must sit alone, as helpless as anyone else, in pain, and unable to be rid of it without sacrificing his vessel."