The Terran Emppire is often a feature of the Mirror Universe. It posits a world where humanity has given in to it's baser instict and has engaged in a reaign of conquest, terror and exploitation of the rest of the galaxy.
The Terran Empire is brutal, ruthless and implacable.
It is also nonsensical. Why would a group of rapacious conquerors designa nd build starships that mirror Federation Starships? Federation Starships are expensive vehicles of exploration and science as well as defense.
How is it possible that random circusmstances in two different histories conspire to populate an unreasonable duplicate of the Federation Starship with Duplicates of it's crew?
The answer is Unfinished