Carnifex is the main antagonist in the Terry Jones short story The Flying King. Carnifex is a demon who lives in Hell and enjoys abducting children to eat, taking them to Hell. He has been doing this for centuries without anyone knowing.

One day, however, he gets up for breakfast in Hell, and finds no children in his larder, because he's eaten them all. Carnifex realizes he'd have to go to another situation about it and he visits a vain king, who has so many children in his kingdom no one would notice if he stole one. Carnifex visits the surprised king when he is getting out of one of his many baths, and Carnifex grants the king the power of flight, and says he'll let the king fly as long as he wants. Only if Carnifex gets a child a day as a reward. Carnifex only tells the king this because the king keeps harassing Carnifex about what he wants in return.

Even the king knows this is an evil deal, so he refuses at first, but, tempted by the power of flight, he eventually agrees. The Faustian deal is made, and Carnifex grants the king the power of flight forever, and the king says Carnifex can take any child to eat from his kingdom any time he wants.

Carnifex comes and goes taking children to eat, and even though the people see the king fly and initially praise him for his power, they soon get bored of it and complain. As Carnifex continues abducting children, sure enough, their parents notice. However the only one with any authority to complain is the queen herself, because the prince is himself taken to be eaten by Carnifex one day. The king isn't bothered, even though he is the boy's father, but the queen goes mad with grief. However, her daughter overheard the Satanic deal done between her father and the demon, and she told her mother. The queen knows if she tells the king about his actions he'd kill her, so she disguises herself as an old beggar woman, and roams the streets with her daughter, spreading the story. Soon, everyone knows the truth, and they all rebel against the king.

The king flies up and summons Carnifex, who appears sitting on the fountain. He actually charms the townspeople with his smooth words, and wise voice, and the ladies begin falling for him, but the king's daughter protests because she knows he's a demon. Carnifex points out he'll repay the townspeople by letting them all fly like the king. But the king's daughter throws her favourite doll onto Carnifex, who had been eyeing it hungrily because he thought it was human, and Carnifex immediately chews it up. The people also think the doll is human and charge Carnifex, who yells in rage, and flies up, dragging the flying king to Hell.

Carnifex continues to return to plead with the people to give him a child to eat, but he is unsuccessful.