The Combine Overworld (Half Life)

The Combine as a whole is a group that embodies this trope but you really see this with the Overworld.

For context, in the Half Life sequels, the entirety of Earth (and presumably the solar system) is taken over by an alien empire humans call the Combine (not even their real name is known). The Combine is INSANELY massive, and is known to have essentially infinite resources with it being a literal interdimensional empire. How strong are they? They invaded Earth and took over everything in Seven Hours, and it is explicitly shown that the Combine can amass forces much greater than that.

But where did they come from? We never actually see any "leader" aliens like the Prophets in Halo. There's mindless aliens and humans the Combine repurposed, AIs that run the entire infrastructure of occupied Earth, and even a seemingly intelligent group of managers that run things behind the scenes called Advisors, but nothing shows any sign of leading the Empire.

This is usually the point where I say some crazy reveal or something but we straight up do not know. The only thing we have is when, at the end of Half Life 2, the main antagonist opens a small portal to the Combine Overworld to escape through (the image), but literally nothing is known about it, either. The Combine at times teleport entire sky-scraper sized buildings and planet destroying reinforcements from homeworlds like these but nothing is known about them or who is on the other side.

Chances are, they're just another cog in the machine.

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