Combine Advisors

The Combine Advisors are the true main antagonists of the entire Half-Life series. They are bio-mechanical emotionless, cultureless, logical beings who enslave, assimilate and exploit all other sentient life for their own purposes, mostly for amoral scientific advancement. They serve as the master race and controlling force of the entire Combine Empire.

The Advisors are responsible for the Seven Hour War, which was the beginning of their invasion of Earth and the conquer of humanity within the aforementioned 7 hours.

Half-Life 2
A single Combine Advisor serves as the Bigger Bad/Greater Scope Villain, occasionally seen on screens giving Wallace Breen orders.

More to be added

Half-Life 2: Episode 1
To be added

Half-life 2: Episode 2
To be added

Trivia

 * It is heavily implied that the Advisors seen are only in their larval form, suggesting that upon hatching they will begin to evolve and grow into far more powerful creatures.