Dominator

The Dominators are an intergalactic sapient species which looks externally indistinguishable from Humans (or Time Lords). They are notable as ruthless conquerors who travel in saucer-shaped vessels which can be powered by radiation; take over planets with the help of their army of robotic Quark servants and enslave species which they find suitable (those which are sufficiently resilient physically but not too intelligent so they would have a better chance of obeying commands without questioning). At an unspecified point in time they had control over much of the region known as the Ten Galaxies. No information is known about which galaxies constituted this empire, and even the period of time the Dominators' government over them lasted.