Klingon-Cardassian Alliance

In the mirror universe, the Klingon-Cardassian Alliance was the historic union of the Klingons and the Cardassians, two former enemies, in the face of aggression from the Terran Empire. Following a series of reforms by Spock, the leader of the Empire, the Alliance conquered the Empire, enslaved Terrans and Vulcans, and became the dominant power throughout most of the 24th century.

A Regent led the Alliance, delegating authority to various Intendants who administered individual sectors of Alliance territory.
 * It is unclear whether the Alliance had a central location of government, on either Qo'noS, Cardassia or elsewhere.

Bajor became a sovereign planet in the Alliance by the late 24th century, after the Alliance liberated Bajor from the Terran Empire.

In the latter half of the 24th century, a Terran rebellion against the Alliance was created due to interference from individuals from the primary universe. 

The Klingon-Cardassian Alliance fell to the Terran rebellion. The rebellion eventually destroyed the Klingons and Cardassians, and evolved into the Second Terran Empire.

The rebels created a new empire which conquered the Alliance by 2385.

In the year 2382, four or five random ships of the Klingon-Cardassian Alliance were given increased power to weapons, shields, and structural integrity. The power was fused upon the vessels by the Pah'Wraith, who were trapped within an ion storm, taking a more active role in the struggle for power in the Alpha Quadrant. The reasons for their involvement are still unknown, but their bestowing of power didn't end with the Alliance as they also bestowed power to one ship in the Terran Empire: the ISS Descent. Only months later, the Descent's abilities were taken away, and the Pah'Wraith's support for the Klingon-Cardassian Alliance was full-fledged.