Undead armies are fictional groups of reanimated corpses or skeletons that serve a master, often found in fantasy literature, video games, and movies. These armies are typically created through dark magic or necromancy, allowing the dead to rise and fight again. They are commonly associated with themes of horror and the supernatural. In many stories, undead armies are led by powerful figures such as necromancers or dark lords. They often serve as antagonists, posing a significant threat to the living. Popular examples can be seen in works like The Lord of the Rings and World of Warcraft, where they play crucial roles in the conflict between good and evil.