Headache.
"Most people say that headaches feel like nails being hammered into your skull. I don't think of it like that. To me, a headache is more like a ravenous beast, crawling into my mind, its weight pressing down, squeezing the life out of my thoughts. It grows, its claws digging in deeper, its jaws tightening around my brain, slowly devouring. It’s not just pain; it’s a hunger, feeding on my thoughts, pulling everything into its black void." - Tomino Infierno