The Havoc Wellhead (sometimes styled Havok Wellhead) is a realm of Oblivion controlled by many Daedric clans in the service of Mehrunes Dagon. It acts as one of Dagon's many provincial governmental centers. It was accessible from the Battlespire, but the connection was lost after its destruction during the Imperial Simulacrum.
The Chimera of Desolation links to this realm via teleportation from the Temple of the Daedric Rites in the walled town of Granvellusa. The castle of Daedra Lord Imago Storm is found here, which houses the gate to Dagon's Hunting Lodge. To activate the portal, the three gatekeys must be inserted into the gate lantern. The realm is the site of many Daedric affairs. An arena stages honorable fights between clans, and "Preliminary Intelligence" tests take place for unknown reasons.
The forces of Mehrunes Dagon used the realm as a headquarters during the invasion of the Battlespire. An apprentice from the Spire arrived in the Wellhead to save a fellow apprentice. The apprentice became an ally of Imago Storm of Clan Dremora, who was opposed to Dagon's invasion. Imago wanted Dagon and his lieutenants banished to the Void, so that he could restore Clan Dagon to stability in their absence. Imago promised the apprentice aid from his Dremora vassals and gave him the neonymics of Dagon, Xivilai and Faydra, which would allow him to banish those Daedra.
The apprentice tracked down the two other Daedra Lords of the realm, Xivilai Moath of Xivilai's Clan and Faydra Shardai of Shardai Clan, tricking and banishing them respectively to get their keys. Before the apprentice could leave, Jagar Tharn's servant Sirran Angada appeared and revealed Tharn's false reign and Dagon's role in it. The apprentice slew him as a traitor to the Empire and used the keys to depart from the Havoc Wellhead.