D: A race in Star Trek which 'assimilates' entire cultures, forcing them to join a collective consciousness which removes all individuality and free thought.

The individuals who get assimilated into the collective become part-organic, part-machine, and live in big cube-shaped space ships.

The Borg do not create any technology, they just assimilate technologies from the cultures they assimilate.

The Borg are the ultimate communist nightmare. The most frightening thing you can hear is a hail from a Borg ship which you cannot defeat or outrun:

You are about to be assimilated into the Borg Collective. You will be assimilated. Resistance is Futile.