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Alien Controllers are levitating Xen creatures. They appear to be intelligent, and closely resemble the Nihilanth but smaller. This, along with their name, suggests they are part of the command caste of the intelligent Xen species. Controllers are not seen in the Black Mesa Research Facility until Gordon Freeman is about to teleport to Xen, where they are encountered in full force. Gina Cross and Colette Green see them more frequently in the facility, during moments of increased resonance displacement activity.


Alien Controller attack

Alien Controllers attacking on Xen.

The Alien Controllers share many characteristics with the Nihilanth, suggesting that they may be closely related. Like other sentient creatures on Xen, the Alien Controllers have a third vestigial arm growing from the center of their chest. In addition to this, the Alien Controllers have disproportionately large heads, which can peel open to reveal a spike or cone, resembling the interior of the Nihilanth's skull. Unlike the Nihilanth, the Alien Controllers have longer legs and are able to levitate without the assistance of a mechanical seat. It is unknown whether this ability stems from their strange psychokinetic powers, or from their seemingly mechanical parts. The Alien Controllers are assumed to have died out after the Nihilanth's death.[1]

Behavior and skills[]

Alien Controller Lambda Complex

Alien Controllers attacking Gordon at Lambda Core.

Alien controller

Alien Controller preparing its energy orbs.

Unlike their master, Alien Controllers do not send telepathic messages to Gordon Freeman. Their language is limited to sounds and various low- and high-pitched screeches and whines when noticing a threat.

They attack by firing multiple spheres of electrical energy (resembling ball lightning) from their hands, in the same way as the Nihilanth. They can also fire an energy ball from their head that is larger and more powerful than the spheres from their hands, and that has a slight homing ability.

Alien Controllers are usually encountered near places where Vortigaunts are made to work. They seem to have an unspoken influence over the Vortigaunts, making them fight or toil at a whim. This is shown at the Alien Grunt cloning facility, where vortigaunts are docile unless the Alien Controllers are present.


  • Unlike most Half-Life creature models, the Alien Controller does not have an HD version.
  • The Controllers' third arm, vertical opening mouths, hoofed feet, molted brown skin, and multiple red eyes all suggest a relationship to the Vortigaunts and Grunts.
  • When launching their homing energy ball, the Controllers will make the same gesture the Nihilanth does when he launches his teleportation orb; hands pushed together, as if they are praying.
  • They only appear once in Opposing Force in which Adrian Shepard can fight some Alien Controllers at Lambda Core (after Gordon Freeman teleports his way to Xen).


List of appearances[]