Tomoe Gozen
In this world, Matt finds several of his deceased friends as well as historical figures, some of whom are his allies and others who are antagonistic. The antagonists include explorer Richard Francis Burton (who in the books was the main protagonist) and Francisco Pizarro, the Conquistador who conquered the Incas. The friendlier people include American author Samuel Clemens (also known as Mark Twain) and Tomoe Gozen, a 12th-century Japanese warrior from the time of the Genpei War married to Minamoto no Yoshinaka. Along with the other heroes, Matt soon discovers that Riverworld has a deeper purpose and is controlled by otherworldly caretakers who are engaged in a civil war.