This book had a lot of things that would be described as extremely gruesome, graphic and horrifying. The protagonist has a terminal disease in which he is turning into a monster, and he routinely vomits up black sludge and parts of his internal organs. He has violent impulses and thoughts that become more and more intense as the story goes on. The cult is also pretty horrible and sacrifices children and cuts them in a ritual way, and uses scarification to put wings into their back. There is also strangulation scenes and scenes where skin and muscle sloughs off the protagonist's body.