Understanding Madness is a quest in Shivering Isles.
Speak to Sheogorath and he will give them the spell Summon Haskill, which makes Haskill a bit glum. They must successfully summon him before one can proceed. Sheogorath will explain to them that Jyggalag, the Daedric Prince of Order (or possibly biscuits), is coming to the Isles to destroy everything in an event known as the Greymarch. He then sends them to meet the aristocracy of his realm, the Duke of Mania and the Duchess of Dementia.
One may meet the rulers in any order. Lord Thadon, the Duke of Mania, can be found in his throne room or painting in the Halcyon Conservatory shortly after 9 a.m. After a bit of Shivering-Isles-esque conversation, Thadon tells you about the Chalice of Reversal, a cup that turns Felldew into an intoxicant. This will activate the quest "Addiction."
Lady Syl, the Duchess of Dementia, can be found in her throne room during the day. Syl is highly paranoid and says that everyone in her employ is waiting for the right moment to "slip a blade into my spine." She then sends the hero off to talk to Herdir the torturer. The quest "The Lady of Paranoia" begins here.
Both Syl's and Thadon's quests must be completed before this quest can be completed.
After completing both quests, speak to Sheogorath again. This will end the current quest and begin the next, "The Cold Flame of Agnon."
|Understanding Madness – SE04Shell|
|3||Sheogorath has given me the ability to summon Haskill. He's very insistent and won't tell me what he wants of me until I do it.|
|5||I need to report to Sheogorath that Xedilian is working, and that Knights of Order have appeared in the Shivering Isles.|
|10||I need to speak to the Duke of Mania and the Duchess of Dementia, as Sheogorath wishes for me to better understand the inner workings of his Realm.|
|20||I have finished Thadon's task. I should now speak with Syl in the House of Dementia.|
|I have finished Thadon's task. I should return to Sheogorath and tell him I've done as he asked.|
|30||I have finished Syl's task. I should now speak with Thadon in the House of Mania.|
|I have finished Syl's task. I should return to Sheogorath and tell him I've done as he asked.|
|200||Now that I've become a member of the courts of both of the Dukes of Madness, I should return to Sheogorath and report my progress.|