After breaking away from the United Alliance of Evil, the Machine Empire arrived to conquer Earth, the final link in a series of conquered planets. The Machine Empire later rejoined the Alliance, only to be destroyed by Zordon's energy wave in Power Rangers in Space.
Once Rita and Zedd were driven away, the Machine Empire set up their base on the moon. Their stronghold housed Sky Fortresses, Quadra Fighters, and several Cogs. The unused Machine facilites remain on the moon.
Mondo, the Machine King
King Mondo is the ruthless leader of the Machine Empire, and not to mention, a loving father and husband.
Machina, the Machine Queen
Queen Machina rules the Machine Empire alongside her husband Mondo, and supports all of his wacky plans to take over Angel Grove.
Mondo and Machina's son, Sprocket is heir apparent to the throne of the Machine Empire, and his father's eager student. Mondo encourages Sprocket to come up with plans to defeat the Power Rangers.
Klank and Orbus
Mondo's two henchbots go down to Earth to supervise many of the Machine Empire's attacks. Upon the defeat of a monster, Klank will hurl Orbus at it, energizing it and making it grow.
Mondo's mechanized army of soldiers. These sophisticated fighting machines are sent down to Earth to battle the Rangers and for espionage and sabotage purposes. They must be either dismantled or short-circuited to be defeated, and they are manufactured at the rate of 1 per hour.
The flying assault vehicles of the Machine Empire, they have amazing speed and firepower, and are piloted by Cogs.
Louie Kaboom was created by Rita and Zedd to take over the Machine Empire after Mondo's destruction. Louie succeeded, but a little too well, leaving Zedd and Rita out of the loop during his conquest of the empire. He was eventually destroyed by the Rangers.
Archerina and Prince Gasket
Machina's first built son and his wife returned in Mondo's absence to destroy the Power Rangers and take over the Machine Empire. They failed at each attempt, and fled back to their home planet when Mondo returned.