Toclafane

The Toclafane (bogeyman in the Time Lord language) of the Doctor Who Universe are the last descendants of humanity, living around the year 100 trillion and wandering across space just as the ‘cold death’ of the Universe began. They are notable for their last-ditch effort at survival: the invasion of Earth, circa 21st century.

History
In the year 100 trillion, the last remnants of Humanity were living in the planet Malcassairo. It is notable that they have reverted to their 21st century form. There they lived in large underground colonies, similar to ant colonies. Due to the “death of all the stars”, Malcassairo was in eternal night, with the colonies being the only refuge from both the cold and the Futurekind, a vicious, carnivorous race roaming the Malcassairo plains for human prey, yet is itself implied to be another human descendant.

In one level of the colony, humans placed their hopes on Dr. Yana, an old scientist, to find a way to leave this last refuge and go to the mythical place of Utopia, a planet known to have been safe from the impending doom. His efforts has led to the creation of a large spacecraft, resembling a giant rocket. Due to the arrival and help of the Doctor, the rocket was made active.

It turned out Dr. Yana was in fact The Master, a renegade Time Lord. He escaped on the Doctor's TARDIS, leaving him and his companions as the Futurekind attacked the base on Malcassairo.

The Master took the Toclafane to the alleged location of 'Utopia', but it was not what they had wished for. The Master showed them to put their heads in the metal cases which became the Toclafane.

The Master used the TARDIS to create a paradox machine, which held the Toclafane in 21st-century Earth. They subdued the population and got them to build a fleet of rockets, to take the Toclafane to the stars in the beginnings of a new human empire.

However, the Doctor and his companions defeated the Master and destroyed the Paradox Machine, trapping the Toclafane at the end of the Universe.