Ur Jan is a supporting character in the story Swords of Mars.
He is the leader of the Zodangan assassins guild. This soon brings him into confilict with John Carter, who has gone on an undercover mission in Zodanga to take down this guild. Both he and Carter get involved in the rivalry between the Zodangan inventors Gar Nal and Fal Sivas when Gar Nal hires Ur Jan to kill Fal Sivas, while Fal Sivas hires John Carter as his bodyguard. Carter does some spying on Ur Jan, learning amon other things that Rapas the Ulsio is giving him information about Carters mission.
When Ur Jan realizes who he is truly dealing with, he and Gar Nal conspire to kidnap Dejah Thoris and bring her to Thuria. After a brief encounter with Carter, the two succeed in their plan. Once on Thuria however, they are promptly taken captive by the Tarids. When John Carter, Zanda and Jat Or follow them to Thuria in Fal Sivas' space ship, they too are captured. The two groups form an uneasy alliance to escape their mutunal enemies. During the escape attempt, Gar Nal double crosses John Carter and abducts Dejah Thoris again in his own ship, leaving Ur Jan behind. Ur Jan himself escapes in Fal Sivas' ship along with Zanda, Jat Or and Umka.
After John Carter also escapes and rejoins the group, Ur Jan swears loyalty to him out of revenge for Gar Nal's betrayal. Back on Barsoom, he accompanies John Carter when the Warlord goes to Gar Nal's house to confront the inventor. After Dejah Thoris is revealed to be there as well, Ur Jan kills Gar Nal.