| image=FileAlien Controller2.jpg|250px
| name=Alien Controller
| type=Vortigaunt warden
| weapons=*Energy orbs (4)
*Homing energy orbs (25)
| entity= monster_alien_controller
| designer=Chuck Jones
'''Alien Controllers''' are levitating Xen creatures. They appear intelligent, and closely resemble the Nihilanth; this, along with their name, suggests they are part of the command caste of the Xen races. 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.
FileAlien Controller attack.jpg|Alien Controllers attacking on Xen.|thumb|200px|left
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 thorax. 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 may have simply died out after Nihilanth's death.http//www.halflife2.net/forums/showpost.php?p=1994259&postcount=847
==Behavior and skills==
Despite their oversized head, and spectacularly-grown brain, Alien Controllers' intelligence is very limited in several aspects. They can not communicate with each other, or any different kinds of specimen on Xen. Unlike their master, they can't even send telepathic messages to Gordon Freeman either. Their language is limited to babbling, 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, more powerful and has a slight homing ability.
Alien Controllers are usually encountered near places where Vortigaunts are made to work. They seem to have had an unspoken influence over the Vortigaunts, making them fight or toil at a whim. This might indicate that the Alien Controllers share a limited version of Nihilanth's psychic enslaving power or act as an intermediary conduit, although their exact role in the hierarchy is unknown.
*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. This can be seen in the picture above.
*The Alien Controller somewhat resembles a "gray alien" of UFO lore.
*They only appear once in Opposing Force.
FileController test map.jpg|Early Alien Controller in a test map.
FileController above.jpg|Alien Controller with its head open, seen from above, Looks related to the spike seen in the Nihilanth.
FileHalfLife_AlienController.jpg|Alien Controller's front view.
FileAlien_Controller_en_el_Complejo_Lambda.png|Alien Controllers attacking Gordon at Lambda Core.
FileAlien_controller.jpg|Alien Controller preparing his energy orbs.
==List of appearances==
*''Half-Life Opposing Force''
*''Half-Life Blue Shift''
CategoryHalf-LifeCategoryHalf-Life Opposing ForceCategoryHalf-Life Blue ShiftCategoryHalf-Life DecayCategoryXen creaturesCategoryChuck Jones designs