Task: Question Answering
Input (English): Mayre Griffiths, nicknamed Trot, or sometimes Tiny Trot, is a little girl who lives on the coast of southern California. Her father is the captain of a sailing schooner, and her constant companion is Cap'n Bill Weedles, a retired sailor with a wooden leg. (Cap'n Bill had been Trot's father's skipper, and Charlie Griffiths had been his mate, before the accident that took the older man's leg.) Trot and Cap'n Bill spend many of their days roaming the beaches near home, or rowing and sailing along the coast. One day, Trot wishes that she could see a mermaid; her wish is overheard, and granted the next day. The mermaids explain to Trot, and the distressed Cap'n Bill, that they are benevolent fairies; when they offer Trot a chance to pay a visit to their land in mermaid form, Trot is enthusiastic, and Bill is too loyal to let her go off without him. So begins their sojourn among the sea fairies. They see amazing sights in the land of Queen Aquarine and King Anko (including an octopus who is mortified to learn that he's the symbol of the Standard Oil Company). They also encounter a villain called Zog the Magician, a monstrous hybrid of man, animal, and fish. Zog and his sea devils capture them and hold them prisoner. The two protagonists discover that many sailors thought to have been drowned have actually been captured and enslaved by Zog. Trot and Cap'n Bill survive Zog's challenges, and the villain is eventually defeated by the forces of good. Trot and Cap'n Bill are returned to human form, safe and dry after their undersea adventure. As many readers and critics have observed, Baum's Oz in particular and his fantasy novels in general are dominated by puissant and virtuous female figures; the archetype of the father-figure plays little role in Baum's fantasy world. The Sea Fairies is a lonely exception to this overall trend: "The sea serpent King Anko...is the closest approximation to a powerful, benevolent father figure in Baum's fantasies." 
Question: What defeats Zog?
Output (English): The forces of good