The Elder Scrolls IV: Shivering Isles is the largest official expansion pack for the role-playing game The Elder Scrolls IV: Oblivion. Announced on January 18, 2007, the expansion was developed, published, and released over the Xbox Live Marketplace by Bethesda Softworks; its retail release was co-published with 2K Games. It was released for Microsoft Windows in a boxed retail edition on March 26, 2007, while the Xbox 360 version was released digitally on the Xbox Live Marketplace. Shivering Isles takes place on the eponymous isles ruled by the Daedric Prince of Madness, Sheogorath. The player becomes Sheogorath's protégé, and together they try to defeat the Daedric Lord of Order, Jyggalag, thus preventing the isles from being destroyed; this main quest can be ignored as long as the player wishes to interact with the new world.