The Flora and Fauna of the Shivering Isles are a testament to Sheogorath's madness, as the north, known as Mania, reflects the Mad God's pleasure with simple madness and calm obsession. This was not until the Last Dragonborn, at the urging of Dervenin, went into the mind of Pelagius Septim III and made the Daedric Prince return to the Isles in 4E 201. During this time, dialogue with Dervenin suggests that the Isles went into a state of chaos without the Mad God's rulership, as according to Dervenin the Cold Flame of Agnon went dark and that north and south raged war, suggesting a civil war took place. Дuring the Fourth era, Sheogorath went on a 'vacation' to the mind of Pelagius Septim III. After being defeated, Jyggalag named the Hero of Kvatch the new Daedric Prince of Madness before departing to wander the voids of oblivion. The person who would later become Sheogorath's champion would be none other than the Hero of Kvatch, who would kill the Gatekeeper, become the Duke or Duchess of either Mania or Dementia and defeat Jyggalag's Forces of Order while defeating the Daedric Prince himself in single combat, thus freeing him from his curse and allowing him to roam the plains of Oblivion in his true form. His purpose was to find a champion who would end the Graymarch. Дuring the year 3E 433, Sheogorath sent an invitation to the Nirn in the form of a large three-headed gate to the Isles located in the Niben Bay. After the trial, Sheogorath had Eyevea returned to Tamriel. With his knowledge, Shalidor assisted the guild in surpassing Sheogorath's trials in the Shivering Isles, in the locations of Cheesemonger's Hollow, the Glade of the Divines, the Circus of Cheerful Slaughter, and the Chateau of Ravenous Rodent. In 2E 582, the Vestige and Valaste of the Mages Guild succeeded in creating a corporeal form of Shalidor's soul. Eyevea was later transported to the Shivering Isles, a decision which Shalidor would come to regret. Sometime during the First Era, Sheogorath made a deal with the famed wizard Shalidor, giving him the Folium Discognitum for his work on Glamoril, in return for the island of Eyevea. Haskill, who would later become Sheogorath's chamberlain, was said to have mantled Sheogorath in an event in a previous time. As a part of his curse after gaining control of the Shivering Isles, Jyggalag transforms back into Sheogorath who then recreates the realm back to one of madness. This event is known as the Greymarch, when Jyggalag destroys the Isles and turns them into the realm of perfect order.

However, at the end of every era Jyggalag is allowed to revert to his original form and wreak havoc in this realm of Oblivion. Since then the Shivering Isles have been ruled by Sheogorath. Because of it, they cursed Jyggalag to live a life of a madman, the thing that he hated most. He was so powerful that the other Princes feared him. The Shivering Isles were once the realm of Jyggalag, the Daedric Prince of order.

The shivering isles nexusmods