Éomer is a fictional character from J.R.R. Tolkien's legendarium, primarily featured in "The Lord of the Rings." He is the nephew of King Théoden of Rohan and serves as the Marshal of the Riddermark. Éomer is known for his bravery and loyalty, playing a crucial role in the defense of his homeland against the forces of Saruman and Sauron. Throughout the story, Éomer becomes a key ally to Aragorn, Legolas, and Gimli in their quest to defeat the Dark Lord. He leads the Riders of Rohan into battle at the Battle of the Pelennor Fields, showcasing his leadership and combat skills. Ultimately, Éomer ascends to the throne of Rohan after his uncle's death, becoming a wise and just king.