Charles Marlow
Marlow's name may be inspired by the Elizabethan playwright Christopher Marlowe. Conrad's father was a translator of William Shakespeare who doubtless would have known of Marlowe's work as well. Some intertextual interpretations of "Heart of Darkness" have suggested that Marlowe's "The Tragical History of Doctor Faustus" may have influenced Conrad. Charles Marlow describes a character as a "papier-mache Mephistopheles", a reference to the Faust legend. Marlow's and Kurtz's journey up the Congo River in "Heart of Darkness" also has similarities to another work by Marlowe, "Dido, Queen of Carthage", in which Aeneas is stranded on the shore of Libya and meets the African queen Dido.
Solomon Kane
"Tales of the Shadowmen" is an anthology series edited by Jean-Marc Lofficier and Randy Lofficier, where characters from French adventure literature exist in the same universe. "Tales of the Shadowmen, Volume 3: Danse Macabre" includes a story entitled "The Heart of the Moon" by Matthew Baugh which features Solomon Kane as one of a group of adventurers visiting Féval's vampire metropolis, Selene. "Tales of the Shadowmen, Volume 4: Lords of Terror" includes a story entitled "The Anti-Pope of Avignon" by Micah Harris featuring Solomon Kane as the central protagonist supporting the Huguenot cause in Avignon.