From Phundahl at their western extremity, east to Toonol, the Great Toonolian Marshes stretch across the dying planet for eighteen hundred earth miles like some unclean, venomous, Gargantuan reptile-an oozy marshland through which wind narrow watercourses connecting occasional bodies of open water, little lakes, the largest of which covers but a few acres. This monotony of marsh and jungle and water is occasionally broken by rocky islands, themselves usually clothed in jungle verdure, the skeletal remains of an ancient mountain range.Little is known of the Great Toonolian Marshes in other portions of Barsoom, for this inhospitable region is peopled by fierce beasts and terrifying reptiles, by remnants of savage aboriginal tribes long isolated, and is guarded at either extremity by the unfriendly kingdoms of Phundahl and Toonol which discourage intercourse with other nations and are constantly warring upon one another.Upon an island near Toonol, Ras Thavas, The Master Mind of Mars, had labored in his laboratory for nearly a thousand years until Vobis Kan, Jeddak of Toonol, turned against him and drove him from his island home and later repulsed a force of Phundahlian warriors led by Gor Hajus, the Assassin of Toonol, which had sought to recapture the island and restore Ras Thavas to his laboratory upon his promise to devote his skill and learning to the amelioration of human suffering rather than to prostitute them to the foul purposes of greed and sin.