Complex sentence: He becomes a partner of Dante as both hunt multiple demons; however, in the novel's climax, he confronts Dante and perishes in their duel, with Dante learning in his final moments that Gilver was his brother.
Split into simpler sentences: He becomes a partner of Dante as both hunt multiple demons. However, in the novel's climax he confronts Dante and perishes in their duel, with Dante learning in his final moments that Gilver was his brother.