Harry Potter and the Deathly Hallows
Xenophilius is Luna's super quirky (would we have it any other way?) dad. In this novel, he serves two primary purposes. The first is to help Harry, Ron, and Hermione on their way to learning more about the Peverell brothers and the Deathly Hallows. The second is to illustrate how Voldemort is tearing families apart and turning friends against one another. Luna is stolen away by Death Eaters, and Xenophilius is willing to do anything to get his beloved daughter back – even turn in Harry Potter to Voldemort. Xenophilius is absolutely a good guy, but he's simply terrified for his daughter in this case.