She was created by Edgar R. Burroughs and appeared for the first time in his novel The Gods of Mars. Phaidor appeared fairly little in many adaptations of John Carter's work, with her role being reduced.
Phaidor is a Thern princess and daughter of the Holy Hekkador of the Therns, Matai Shang. She is kidnapped by First Born pirates during events of "The Gods of Mars". When John Carter is taken alongside her to the Temple of Issus, she falls in love with him when he protects her from the First Born pirates. Phaidor tries to seduce Carter, but she is spurned when he reveals he is already married to Dejah Thoris, Princess of Helium. Phaidor is taken to be Issus' handmaiden for one Martian year, where after that she is expected to be devoured by the Living Goddess. When John Carter manages to incite a revolt and escapes, she is imprisioned inside the Temple of the Sun along with Dejah Thoris and Thuvia of Ptarth (who also was in love with John Carter). Insane with jealousy, Phaidor tries to kill her in front of Carter as the Temple of Sun closes its door in front of him. She is unsuccessful however and is stuck there with two other Red women waiting a year for the entrance to open again. Eventually, she warms up and forms a strong bond with them.
They are freed by her father, who has broke a uneasy alliance with Thurid of the First Born, to use a secret entrance into the Temple to liberate the captive princesses. Dejah and Thuvia were bound by the Shang, as he intended to torture and punish them to hurt Carter for interfering in his plans. Phaidor tried to stand up to Dejah Thoris and protect her from her father's rage to little avail. When a argument broke out between Salensus Oll, Jeddak of the Yellow Martians and Matai Shang over who would have Dejah as their concubine, the Okkar lord killed her father before her eyes. Phaidor was taken to be Oll's concubine along with Dejah and Thuvia, but this turned out to be his own undoing as during the Red Martian attack on Okkar, the three women took advantage of the confusion and stabbed to death, with Phaidor avenging her father Shang's death.
Their victory was short-lived, for immediately after killing the yellow tyrant, both Phaidor and Dejah were captured by Thurid, who escaped on a ship, hoping to take the two women as his prizes. When John Carter gave chase, Phaidor took advantage of Thurid, while he was gloating about he was going to do with his wife, causing him to fall to his death. After seeing the couple reunited, Phaidor wanted to repent for all the wrong she caused and jumped to her death.
John Carter's Gods of Mars
In Marvel publishing, her role is similar to the one in the books, but is greatly reduced. She is captured by the First Born and taken along with John Carter before Issus to be made her slave girl. She is not seen anymore beyond this point.
Phaidor is wicked, shallow, jealous, proud and vindictive. Like the rest of her kind, she believes all life in Barsoom to be beneath the Therns. To show how proud she is, Phaidor refers to herself as the Daughter of Matai Shang to showcase her position and title. Despite this, she isn't incapable of affection and love; Phaidor is attracted to John Carter (despite he being a Earthman) after defending her from the Fist Born pirates while they are captive, and she greatly loves her father as she avenges his death after he is betrayed by Sallensus Oll. She eventually realizes her how shallowness and cruelty during her captivity in the Temple of the Sun and tries to repair the wrongs she had done, by protecting Dejah Thoris from her father's wrath, the same woman she tried to kill before for already having John Carter as her husband.
Phaidor is a White Martian, like other humanoid races in Barsoom, they are functionally immortal and long-lived and possess certain psychic affinity. The Therns, as they are known, resemble Caucasian humans with fair skin, blue eyes and blonde hair, though in fact they are all bald and they wear wigs. While in the books, its never outright stated that Phaidor or female therns are hairless like their male counterparts, in the comics she has blonde eyebrows indicating that she is genuinely blonde haired. Phaidor is not technically a princess in a conventional sense or referred to as such, since her father's rank of Hekkador is that of a holy priest rather than a chieftain or monarch.