Kamen Rider Eternal is a character from the Kamen Rider franchise, specifically introduced in the film "Kamen Rider W Forever: A to Z/The Gaia Memories of Fate." He is known for his unique ability to transform using the Gaia Memories, which are special devices that grant powers to their users. Eternal is portrayed as a powerful and enigmatic figure, often serving as an antagonist in the story. The character is associated with the Kamen Rider W series, which features two protagonists who can combine their powers to become a single hero. Kamen Rider Eternal stands out due to his dark and complex nature, making him a memorable addition to the franchise's extensive roster of characters.