There was once a nameless town on an oasis formed by outlaws, and who lived in homes inside a large black market. The market sold all kinds of insane and cursed artifacts which attracted the attention of evil and questionable spirits. They got the attention of The Black Market God which pushed them towards dealing in even worse goods until the entire town was cursed and became a liminal space between the physical world and cursed planes of existence.
Eventually, a man was seen by a female djinn that he saw while visiting the oasis, and she disguised herself as a human to try and seduce the man to break up his marriage. It did not work, but in response she was able to curse the town. She broke into the souk and looked for the worst, most cursed artifact in the market which was a red grail stolen from a god of lust and gluttony. She picked up the glutton’s grail and threw it into the oasis of the town, and the glutton’s grail curse would begin affecting the people of the nameless town. They had an intense desire to cannibalize each other, perform oral sex, or otherwise indulge in debauchery. They were only able to eat meat, bones, dung, or milk without feeling sick, and they would quickly lose a lot of weight and become sick and scrawny if they did not consume excessive amounts of meat.
In previous eras they would eat any humans or animals that wandered into the town, but this would be too suspicious in the modern era. Now, they can only cannibalize migrant workers that they invite from South Asia or The Philippines. The grail still exists at the bottom of the lake, and as long as water touches it its curse will continue. Some have fled the town, but others have stayed and attempted to have children or families. Unfortunately for them, they give birth to monsters or cannibal children that are born with sharp black claws where their nails should be.