Xasoom (known to Earthmen as Saturn, and by its inhabitants as Strio) is the sixth planet from the sun, located beyond Sasoom, which puts it firmly beyond the range of Barsoom's explorations. It had two known sentient races, the Vathek and the Palidor. It was one of the first worlds to develop ships with the capacity for interplanetary travel, with the Vathek sending scouts to Barsoom (or Rautt, as they called it) centuries before the arrival of John Carter.
Dejah Thoris was brought to Xasoom during her period of exile in the wake of the Boora Witch incident, having been captured by one of the scouting missions. While there, she learned of a plot by the Vathek to invade Barsoom, believing that Red Martians would provide them with a new source of sustenance. Aided by the oppressed Palidor and a Vathek defector named Dagur Andlaust, Dejah Thoris foiled the Vathek's plot and managed to return home.