An antagonist is a character or force in a story that opposes the main character, known as the protagonist. This opposition creates conflict, which is essential for driving the plot forward. Antagonists can be villains, like Darth Vader in Star Wars, or they can be more complex characters with their own motivations and struggles. In addition to characters, an antagonist can also be an idea or situation that challenges the protagonist. For example, in a story about overcoming fear, the antagonist might be the protagonist's own doubts. This dynamic helps to highlight the growth and development of the main character throughout the narrative.