The Interregnum was a period in Tamriel's history between the end of the Second Empire and the proclamation of the Third Empire by Tiber Septim. It began when the last of the Akaviri Potentates, Savirien-Chorak, and all of his heirs were murdered by the Dark Brotherhood in 2E 430. The collapse of central authority led to five centuries of bickering between racial alliances, small kingdoms, and petty states. During this time, the Empire of Cyrodiil existed by name only, and was confined to the region of Cyrodiil alone.
The Interregnum was marked by a general decline in living standards across Tamriel. A note in one tale from the era goes so far as to call the prevailing attitude one of "anti-intellectualism", another source talks of the "dark and cumulative losses" of the period, and a third describes the period as "days and nights of blood and venom". A further sign of intellectual decline was the transformation of the Dwemer in popular culture from a mysterious and unfathomable race to a mere vehicle for light comedies and romances. Additionally, roads and cities fell into ruin and were not repaired until centuries later. Even the famed Amulet of Kings was lost.
Some regions and organizations found the period full of opportunities. The services of the Dark Brotherhood were much in demand and the society filled its coffers with gold. High Rock, an area with a history of factionalism was more able to deal with the collapse of central power and fared much better than the rest of Tamriel, lapsing back into its usual structure of kingdoms and city states without difficulty.
However in 2E 541, an invasion of Reachmen under the command of Durcorach swept through the kingdoms of High Rock, ultimately resulting in the signing of the first Daggerfall Covenant. United, the new Covenant was strong enough to repulse and destroy Durcorach's Horde, while a strategic alliance with Hammerfell and the promise to restore Orsinium as sovereign territory cemented the political longevity of the Covenant under the tactful leadership of High King Emeric. Meanwhile, a similar threat appeared to northeastern Tamriel, as an Akaviri invasion in 2E 572 under the command of Ada'Soom Dir-Kamal ravaged the lands of Skyrim and Morrowind. After a long-fought battle and the aid of Argonian reinforcements, the Ebonheart Pact was formed, creating an alliance between the previous Imperial Provinces of Skyrim, Morrowind and Black Marsh. Despite the tensions between the races, the threat of the now corrupt Imperial rule in Cyrodiil maintained the necessity of the Pact to secure their homelands from foreign occupation. In Alinor, the well-traveled High Elf Ayrenn emerged to the throne of the Summerset Isles in 2E 580. Conveniently, the nearby provinces of Valenwood and Elsweyr sought allies against an increasingly chaotic rule in Cyrodiil, thus joining Queen Ayrenn in the first Aldmeri Dominion.
In the heartlands of Cyrodiil, Varen Aquilarios of Chorrol led an uprising against the Emperor Leovic, grandson of Durcorach, after Daedric worship was legalized in the Empire. Leovic was subsequently executed by Varen himself, who then set out on a quest with four companions to recover the lost Amulet of Kings. Secretly, Varen was fearful that his lack of being Dragonborn would ultimately lead to his demise as he thought he was an imposter for not being one of the Dragon Blood. The Altmer Sorcerer Mannimarco persuaded Varen that he knew how to perform a ritual with the newly found Amulet of Kings which he assured would give Varen his much sought-after title of Dragonborn. However, Varen was unknowingly tricked into breaking Alessia's divine covenant with Akatosh, and thereby destroying the ancient barrier between Nirn and Oblivion in an event known as the Soulburst. With Varen now missing, Mannimarco began ushering in his true master, Molag Bal, who planned to draw all of Tamriel into Coldharbour in an event that the Elder Scrolls call the Planemeld. Clivia Tharn, in Varen's absence, became Empress Regent and allied with Mannimarco, but her father Abnur despised the sorcerer, leading to a split in the family and Abnur's subsequent capture. With this, the Empire crumbled into a state of disarray as corruption ran rampant and Dark Anchors began to appear in the skies across Tamriel. In 2E 582, with Imperial Power crumbling, the Daggerfall Covenant, Aldmeri Dominion and Ebonheart Pact vied for control of the White-Gold Tower in the Three Banners War, in an effort to destroy the faltering Empire and restore peace and prosperity to Tamriel.
During the entirety of Interregnum, petty warlords had attempted to seize control of Cyrodiil's capital and to reestablish the Empire. None of them lasted for long, until, in the year 2E 852 the king of Falkreath, Cuhlecain, sought to proclaim himself "Emperor of All Cyrodiil". Two years later, with the help of his general Talos who reclaimed the Amulet of Kings, he took the Imperial City from the battlemages of the Eastern Heartland, but was assassinated shortly after. It is uncertain whether or not Cuhlecain was ever crowned Emperor. The Third Empire was certainly established when Talos took the name Tiber Septim and was crowned in his stead in 2E 854, signaling the end of the Interregnum, although the rest of Tamriel did not submit to his rule until the conclusion of the Tiber Wars in 2E 896.