Emperor Manuel I is the most significant historical figure with whom Kerbouchard comes in contact because of his significant changes and contributions to the Byzantine Empire. Not only does he reign over Constantinople, but his power influences many of the places to which Kerbouchard travels.
Next, Andronicus Comnenus is the cousin of Manuel I and served as the Byzantine emperor, too, although he was exiled. He assists Kerbouchard in some of his activities because he is intrigued by him.
Finally, rather than list another historical figure who is significant from the novel, the places and archetypes whom Kerbouchard experiences or meets are more important. L'Amour includes a vast array of historical "types" such as a Viking, Emperor's guard, a cunning Barron, a powerful prince, etc. These archetypes and the regions with which they are associated play major roles in the novel's themes and characterization.