The Elder Scrolls IV: Oblivion Remastered comes with all of the DLC from the original game, and that includes the Shivering Isles expansion. While there's already a ton of stuff to do in Cyrodiil, Shivering Isles adds over 30 hours of additional quests and exploration in a whole other map zone...
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How to begin The Shivering Isles in Oblivion and the remaster
Source: PC Gamer (opens in a new tab)