Clavicus Vile's Realm

Clavicus Vile's Realm is one of the Planes of Oblivion created and ruled by Clavicus Vile, the Daedric Prince of Deals. It is described as an idyllic countryside, dotted with merchant utopias, twisted foliage, and odd melted-looking places. The air smells like both perfume and rotting flesh, while the sky is blue with cottony clouds and greenish-gray streaks that stain the atmosphere.

Second Era
During the Second Era, a Redguard by the name of Cyrus visited Vile's realm to save his sister's soul, as a Sload Necromancer named N'Gasta had given it to the Daedric Prince. Cyrus managed to outsmart Clavicus Vile and save his sister, Iszara.

Third Era
Near the end of Third Era, Clavicus Vile tasked the Hero of Kvatch with retrieval of a sword called Umbra which contained the soul of an adventurer who had made dealings with Vile in the past. However, Barbas, the Hound of Clavicus Vile, foresaw the destruction it could bring Vile's domain, so he attempted to stop the retrieval. The sword contained a fraction of Vile's power which became self-aware and, if returned to Vile's realm, the being trapped inside of Umbra would be able to steal an incredible amount of power from the Daedric Prince. Unfortunately, Barbas failed. To prevent Umbra from leaving its realm with a portion of his power, Vile closed off the borders of his realm, trapping Umbra within.

Fourth Era
At the beginning of the Fourth Era, a veil was opened into the realm by a device called Ingenium, created by a Dunmer named Vuhon. The veil absorbed power from Vile's realm to prevent the Ministry of Truth, a giant floating satellite, from crashing into Vivec City after the disappearance of Vivec, one of the members of the sacred Tribunal. Vuhon forged a pact with Vile--As long as Vuhon would keep bringing him the souls of mortals, Vile would allow for the veil to be open, preventing the Ministry from crashing into Vivec City. In the meantime, Umbra's curiosity about the veil escalated, as the veil began to widen when the Ingenium was destroyed. Since he was unable to leave the realm, Umbra threw the Umbra Sword into Tamriel to prevent Clavicus from trapping him within it. At the same time, Vuhon was pulled into the Vile's realm where he forged a deal with Umbra. They decided to create another, second Ingenium, capable of escaping Vile's circumscription. Another part of the deal was that Vuhon's life would be spared. When the second Ingenium was constructed, Umbra used its power to rip away part of Vile's realm, which was set lose into the Void.

This separated piece of Vile's realm appeared to be like a floating mountain and had an elegant city on top of it. The floating island was named Umbriel and had a unique variation of Hist Trees, called the Um-Hist, which resembled those found in Black Marsh. It was eventually banished by the power contained in the White-Gold Tower in the 40th year of the Fourth Era. Whether Clavicus Vile's Realm ever recovered from the ordeal is still unknown.