Vor Daj is the protagonist of the novel Synthetic Men of Mars.
He is a padwar of John Carter's personal troops and the Warlord's chosen companion when he goes in search of Ras Thavas who is Carter's only hope for healing the terrible injuries of his beloved Dejah Thoris. Captured by the Hormads of Morbus they find the man they want is also there, a prisoner of his own creations, and Vor Daj falls in love with another captive the lovely Janai. Desperate to save her from the lustful clutches of the Hormad Jeds he goes so far as to have his brain implanted in the abandoned Hormad body of Tor-dur-bar. Being like most of Burrough's heroes an idiot about women he does not tell Janai his true identity for fear that she will continue to see him as the horrible Hormad even after he returns to his own body.
When John Carter and Ras Thavas escape through a secret tunnel and plan to make their way back to Helium, Vor Daj stays behind to look after Janai. He wins the favor of the Third Jed when he helps him become Ay-mad, Jeddak of Morbus. He is made a dwar in the army of Ay-mad, and put in charge of the laboratory, but without Ras Thavas around things soon go horribly wrong and a large pile of ever growing flesh, heads and organs emerges from Vat Room 4, threatening to engulf all of the city. Vor Daj has his body and the brain transfer equipment hidden in the same secret room John Carter and Ras Thavas escaped through. Then he, Janai, and three men named Sytor, Pandar, Gan Had, the former owner of Tor-dur-bar's body who now calls himself Tun Gan, and a Hormad named Teeaytan-ov flee Morbus and try to make their way through the Toonolian Marshes.
Several adventures follow, in which Vor Daj and Janai first end up with the Kangaroo Men, and are later captured by soldiers from Amhor. Vor Daj, still in the body of a hormad, is put on display in the zoo of Amhor while Janai is taken to Jal Had, the jeddak, who plans to marry her. Vor Daj manages to escape and along with the Green Martian Bal Tab and the slave Orm-O he manages to free Janai. During their escape Bal Tab is killed, but Vor Daj and Janai are rescued by the fleet of Helium that was on his way to Morbus. Back in Morbus the Hormads and the monstrous flesh-creature are defeated, after which Vor Dai gets his old body back. By now Janai has already guessed the truth that Tor-dur-bar was Vor Dai al along. And while she admired Vor Daj's fine body on their first meeting it is his chivalrous soul she truly comes to love even in a Hormad body.