Hoshi Sato is a villainess who went from I.S.S. Enterprise Communications Officer and Captain's Woman to Empress of the Terran Empire In Star Trek: Enterprise.
Her Rise to Power
Serving mainly as Captain Forrest's woman, Sato had previously been involved with Jonathan Archer but left him for Forrest when he was promoted to a position of higher power. When Archer briefly took command of the Enterprise in 2155, she gravitated towards him again as he was then the more powerful. While making advances towards Archer, she made an effort to stab him with a dagger, but her attempt was thwarted. Later, after she and Archer had made love, she casually proposed that T'Pol, not Tucker, might have had a hand in sabotage aboard the ship, making Archer realize that he should have suspected T'Pol as well. However, T'Pol had already led an insurgency to restore Forrest to command.
Sato was aboard the Enterprise when it was trapped in a Tholian web, though she was able to evacuate on an escape pod before the ship was destroyed and was picked up by the commandeered USS Defiant. (ENT: "In a Mirror, Darkly")
Sato assisted Jonathan Archer in using the Defiant to gain power. However, before the Defiant could make it to Earth, she seduced Archer's personal guard Travis Mayweather into conspiring to kill Archer by poisoning him. Sato subsequently took command of the Defiant, proclaimed herself "Empress Sato", and ordered Fleet Admiral Gardner to surrender and stand by for instructions, or she would open fire on Earth.
Her Reign and The Sato Dynasty
Sato established her imperial residence in the historic Kyoto Imperial Palace. One of her primary goals as ruler of the Terran Empire was to crush the rebel forces arrayed against the Empire. Toward this goal, Sato arranged to be married to General Thy'lek Shran of the Andorian Imperial Guard, thus creating an alliance and cutting off a key source of rebel support.
She also ensured that the true nature of the starship Defiant was kept secret, claiming it was from the Empire's future, rather than from a parallel universe where the Empire never existed. She also fabricated several "historical" facts she claimed to have found in the Defiant database, including the birth of a child to herself and Shran.
When Shran discovered the Defiant's true nature, he arranged to have Sato's ova taken from her, a child artificially gestated from their joined DNA, and then sent Sato into exile, while he took control of the Empire as regent for their unborn child.
Sato was sent to Deneva, but her transport was intercepted by Vulcan rebels. She was held prisoner, and then put on trial for the crimes of the Empire against its subject worlds. However, Sato was able to strike a deal with one of the rebels, and her former Enterprise crewmate, T'Pol. By helping her escape the rebels and helping reclaim the Empire from Shran's Andorian forces, the people of planet Vulcan were then raised to a status equal to that of humans.
Sato personally executed the scientist Arik Soong, which halted scientific progress with artificial life-forms indefinitely. Noonien Soong speculated, decades later, that this may have been one of the factors that led to the Empire's demise.
Sato's line continued to rule the Terran Empire until 2277, when Hoshi Sato III was usurped by then-Grand Admiral Spock.