In the mirror universe, Betazed is the homeworld of the Betazoid people.
The Terran Empire conquered Betazed in 2230; however, many of the early imperial administrators, and their lackeys, died strange deaths at the hands of the Betazoids who used a form of psychic resistance to challenge their new-found masters. Starfleet Captain Jack Beatty was the first to develop the mental discipline necessary to stave off attacks from the local population. Captain Beatty opened his mind to then-Supreme Leader Giliana Houn where he exposed her mind to the full violence and peversity of the Human consciousness; she suffered a series of devastating strokes and died on the spot. Starfleet Academy taught the Beatty Method to a select number of personnel, including civilian administrators destined for Betazed. Only about 25% of the Terrans residing on Betazed knew the method; nevertheless, it was high enough to keep the Betazoids from attempting to enter the minds of their Terran occupiers.
Learning to accept their fate, the Betazoids quickly sought to raise their status within the empire by offering their thought-invading abilities to Imperial Starfleet. Still, Humans remained weary of the Betazoids and their intentions for at least another fifty years before raising the planet's status to that of vassal in 2278.
While a vassal in the empire, Betazed was a police state where the minds of the strong dominate those of the weak. Beginning in childhood, all Betazoids learned to either shield their minds from the intrusion of others, or to steal thoughts from weaker minds.
Betazoid society remained matriarchal with women commanding households, and dominating the top positions in most organizations, demanding sexual favors from men. Betazoids continued to practice their bizarre orgiastic, and nude, wedding ceremonies, drenched in the blood of freshly-slaughtered animals.
With the rise of the Klingon-Cardassian Alliance, Betazed suffered greatly due to being a world of some status in the Terran Empire. Deanna Troi began the resistance on Betazed. Treated as a second-class citizen due to her half-Terran ancestry, she had a history of criminal activity from a very early age. Between 2369 and 2370, she shifted her attention from crime to open rebellion, mobilizing her criminal contacts, and throwing her support behind the emerging Terran Rebellion. In 2372, "Intendent" Troi as she sometimes refers to herself, bribed and killed her way onto the Alliance's Betazed Orbital Construction Station where she and her accomplices made off with several nearly complete Alliance warships. Using the ships, she managed to capture and hold several planets in a system near to Betazed. She has since teamed up with the rebellion forces in control of Terok Nor. (RPG reference: Through a Glass, Darkly)
The status of Mirror Betazed depends upon the source. While Through a Glass, Darkly has it conquered and subjugated by the Terran Empire, The Sorrows of Empire indicates that the Betazoids had all but been exterminated by the empire due to their telepathic abilities. Still another, The Sacred Chalice, takes places on a ruined Betazed, circa 2371, where the remnants of the Betazoid race eek out a meager existence.