Origin
Osor is a Green Martian and member of the Warhoons.
Major Story Arcs
Dejah Thoris had gone undercover as a Red Martian slave to stop the Warhoons from using a weapon which would destroy Helium and Thark, and while pretending to be a slave, she became friends with several of the Warhoons, including Osor. Osor was opposed to using the weapon on the Tharks and Red Martians.