Prince Khaemwaset, also known as Setne, is an anti-hero-turned-major antagonist in Rick Riordan's 2012 novel The Serpent's Shadow, as well as the main antagonist of the collection of short stories known as Demigods and Magicians.
Setne was the son of Ramesses the Great. In his life, he committed many crimes such as breaking into tombs, fighting as well as blaspheming gods, and stole the Book of Thoth. Before his death, he created a shadow execration spell that could be used to kill Apophis. Setne planned to blackmail Apophis into only destroying what Setne wants him to, but was thwarted by his own death. Even after his death, Setne continued to lie to and deceive people. He executed various schemes to avoid his trial in the Hall of Judgement.
The Serpent's Shadow
Carter and Walt talk to Thoth and find out about Setne and how he could help them figure out the shadow execration spell. Carter, Sadie, Walt, and Zia go to the Hall of Judgement and watch as Setne begins his trial. Carter and Sadie explain the situation to their father and convince him to let Setne go with them on their quest.
While Sadie and Walt go to find Bes' shadow, Setne guides Carter and Zia to the tomb where he hid the Book of Thoth. After defeating a giant hippo and the Apis Bulls, they escape with the Book of Thoth and go to the Land of the Demons. Setne gives Bloodstained Blade, the Kanes' ship's demon captain, permission to attack and kill Carter. Carter and Zia kill Bloodstained Blade and capture Setne as he tries to escape.
Setne casts a glamour spell on Carter and Zia to make them blend in with the rest of the demons. He leads them to the sea where Apophis' shadow is held down by a powerful obelisk on Ma'at energy. Carter and Zia are able to capture Apophis' shadow, but Setne captures them by turning their glamours into bindings. Sadie arrives, frees Carter and Zia, and ties Setne up in the Ribbons of Hathor. The trio hauls Setne away, but are attacked by an army of demons. While they are being rescued by Bes, Tawaret, and the gods from the House of Rest, Setne escapes with the Book of Thoth.
Demigods and Magicians
The Son of Sobek
In this short story, Percy Jackson and Carter Kane battle a giant moster crocodile. It is later revealed that the giant crocodile was summoned by Setne as an attempt to combine Greek and Egyptian magic.
The Staff of Serapis
After defeating the god Serapis, Sadie Kane and Annabeth Chase suspect that Setne was behind Serapis' rampage. It is later revealed that they were correct to assume so.
The Crown of Ptolemy
Setne causes a freak hurricane in Manhattan as he summons Wadjet to steal her crown of Lower Egypt. He destroys Wadjet by consuming her essence, but not before taking a selfie with her to "remember" the moment.
Percy and Annabeth pursue Setne and try to kill him, but to no avail. Setne nearly overpowers them, but Percy and Annabeth are rescued by Carter and Sadie. Setne escapes and summons Nekhbet to steal the other half of Egypt's crown. Percy, Carter, Annabeth, and Sadie arrive to stop him, but they are too late; Setne escapes with the now-complete crown of Egypt.
Annabeth, Sadie, Carter, and Percy (who has merged with Nekhbet) follow Setne and attack him. Setne taunts Carter about his father and mocks Percy for turning down the gods' offer to make him immortal. Percy, Carter, Annabeth, and Sadie strip Setne of his crown and imprison him in a snow globe.