wilds of Denduron; the ocean-wide planet of Cloral; First Earth (the approximate time and location of the 1937 Hindenburg disaster); the virtual-reality wastelands of Veelox; the rainforests of Eelong; the deserts of Zadaa; the corporate monopoly-controlled arenas of Quillan; the semi-civilized island of Ibara (located on the planet Veelox, though 300 years after the "Veelox" territory); Second Earth; and, lastly, Third Earth (New York City in the year 5010). Along his journeys, Bobby also learns martial arts, sometimes even dueling with Saint Dane one-on-one. Bobby also comes to respect the diverse peoples of Halla, who wildly differ in their social structures, technologies, philosophies, traditions, and other cultural aspects. He also has to adapt to each territory's environment to be ready to confront Saint Dane at a moment's notice. Bobby gradually learns the nature of what it really means to be a Traveler, first hinted at when Saint Dane mysteriously begins referring to the Travelers as "illusions". Saint Dane's long-term strategy also eventually surfaces, centering on a mysterious event called "the Convergence", in which the territories' turning points all begin to coincide, potentially causing an escalating chain reaction of chaos throughout Halla. Matters worsen when the Traveler from Quillan, named Nevva Winter, treacherously defects to Saint Dane's side. Meanwhile, the Convergence causes some territories to undergo a devastating and unanticipated second turning point. By the ninth book, Bobby and his friends have successfully prevented the destruction of five territories, but they have failed in their fight against Saint Dane on Second Earth, Veelox, Ibara, and Quillan. Even worse, by overrunning Second Earth, Saint Dane manages to reverse all previous Traveler victories, allowing him to establish an elitist and genocidal cult called Ravinia. Ravinia openly marches its robot army of humanoid soldiers, "dados", throughout the territories, freely breaking down the boundaries between the territories. In the tenth and final book, Bobby finally learns about the true nature of Travelers: that he and the others are not actually humans at all, but rather, human-shaped guardian spirits created by something called Solara: the accumulated energy of all positive sentient knowledge and creativity. Contrarily, Saint Dane is a spirit arisen from a dark antithesis of Solara. Reuniting one last time, Bobby and the Travelers confront Saint Dane in a final battle on Third Earth to begin Halla's process toward recovery at last. Terminology MacHale uses a variety of terms and ideas for the series, which