How do you start the shivering isles in oblivion?

Answer 1

(NOTE: You can only start this if you have purchased and installed "The Shivering Isles" expansion pack for Oblivion) After spending some time in the game, a pop up will appear and say that you have heard a rumor about a strange door in the middle of a lake. It will automatically add it to your quests. Once you arrive at the door, random statements can be heard coming from the door, as well as people who seem to have been driven mad. After a while, you can enter. Inside you will find a man who will explain the door and why it opened. He will ask if you want to go inside. If so, say yes. You will then be able to enter The Shivering Isles.