The Doctor, a Emergency Medical Android
The Doctor was created in the early 2360s by the Empire. The EMA, properly known as the Emergency Medical Android, was developed by a team of engineers to be an emergency supplement to the medical team on starships. It was capable of treating any known injury or disease; programmed with medical knowledge of every member world in the Empire (at least, as of 2371), it had the knowledge of five million surgical treatments and was capable of adapting to create new medical treatments. It also had a database of spiritual medical treatments practiced by Native Americans. It was created on Jupiter Station, by Lewis Zimmerman (on whom the android's appearance and voice were based). Lieutenant Reginald Barclay also worked on the project, testing the EMA's interpersonal skills.
In 2371 The Doctor was assigned to Voyager by Captain Kathryn Janeway as chief medical officer. Voyager was assigned to track down and eliminate all rebel Maquis activity inside the Badlands and in order to begin Imperial expansion and subjugation of the Delta Quadrant. Shortly after entering the Badlands, Voyager was pulled 75,000 light years across space into the Delta Quadrant by an entity known as the Caretaker. Eventually it was revealed that the Caretaker had pulled Voyager across the galaxy in the hopes of finding a people who could care for the nearby Ocampa. Despite his benevolent approach, Captain Janeway saw the opportunity to use his technology to enable the Terran Empire to conquer the galaxy, and she put the Caretaker to death after her crew learned of how his technology functioned. The Doctor developed biogenic weapons during the Vaskan-Kyrian war in 2374 and tortured prisoners with a neural solvent to gain tactical information for the ISS Voyager.
In 2379 The Doctor was part of the plan to kill Empress Hoshi Sato III and Kathryn Janeway would become Empress of the Terran Empire. However, Typhuss was only using the relationship with Hoshi Sato, in order to help Kathryn Janeway assassinate Empress Sato III.