Half-Life Wiki
Half-Life Wiki
This subject is from the Black Mesa Incident era.
Wiki cleanup This article has yet to be cleaned up to a higher standard of quality.
You can help by correcting spelling and grammar, removing factual errors, rewriting sections to ensure they are clear and concise, and moving some elements when appropriate. Visit our Cleanup Project for more details and, please, notify the administrators before removing this template.

"Fire the rocket engine... destroy the damned thing before it gets any larger!"
Black Mesa Scientist[src]

The Tentacle (taxonomic designation: Hypersuctor sensitiva[2]) is a large alien creature which will respond violently to sound and vibrations. It is first seen in a rocket propulsion test chamber but is also seen through the series on Xen and in other areas of the Black Mesa Research Facility, and its juvenile form in City 17's Quarantine Zone.


Tentacle pit

The three Tentacles in the chapter Blast Pit.

A large, green, segmented stalk supports a "head", which ends in a sharply pointed, blade-like appendage and features what looks like an eye similar to the Vortigaunt. This "eye" appears to be a sensory organ, although the creature only reacts to sound and surface vibrations. Tentacles usually emanate from pits, into which they can retract when injured or in danger. Despite this, however, they are incredibly resilient to regular weapons.

Typically several Tentacles use the same pit, suggesting that they may be appendages of a larger organism. Indeed in Half-Life, after the first Tentacle encounter, the player travels through the chasm the creature had occupied. The Tentacle's body encountered at the bottom of the chasm is somewhat squid shaped, with three stumps that appear to have been severed. Some concept art of the Tentacle shows it to be a cluster of three Tentacles attached to a bulbous base, which matches that encountered in the game.

Although Tentacles usually come in groups or clusters of three, single Tentacles are also encountered, and the number of Tentacles present may reflect the size or stage of development of the base, or else a more spread-out being, with Tentacles in various locales. Reasons that could support this assumption are how the Scientist pulled from the control room, when first encountered in the silo, is pulled down into the pit and possibly eaten by the base. Another characteristic could be how it relies on echolocation, as the base could be too large to fit through, and relies on keen hearing to pull prey down.


Throughout the Half-Life series, only ten Tentacles have been encountered, of which eight are found in Half-Life while the other two are found in the expansion game Opposing Force.


In Half-Life, the first encounter is in the chapter Blast Pit where the player encounters three tentacles in a Rocket Propulsion Silo in Sector D. These tentacles act as a sort of boss, which Gordon must destroy via a series of puzzles as they can't be damaged. As the tentacles rely on sound and vibration to locate their prey, Gordon can toss grenades to distract them temporarily. Gordon moves through the silo and reaches other areas that branch off from the silo so that he can switch on the Oxygen, Fuel, and Power for the Rocket Engine. After that, he again must risk through the same Silo back to the Control Room and Activate the Rocket Engine test fire. The heat emanating from the engine destroys the Tentacles and allows him to advance further.

A Tentacle is later encountered in the chapter Surface Tension. It is found living in a small sandy area in the canyon, emerged from a burrow under the sand. Health, ammo and other supplies closely surround its base, and Gordon must sneak up to a dangerous proximity of the Tentacle if the player chooses to retrieve them.

Later, a Tentacle is found in the chapter Interloper, after the first teleportation in that chapter. In this appearance, the player can observe the tentacle in its natural habitat on Xen. It is found outside a cave where the player teleports in. In an area not far from there, three more Tentacles are present, with a circular rocky bridge formation surrounding them. This is Gordon's last encounter with the Tentacles and the player has to distract and sneak past them in order to progress.

Half-Life: Opposing Force[]

In Half-Life: Opposing Force, only two Tentacles are encountered. It is in the chapter Vicarious Reality where the player finds them in an Incomplete Observation Area. The player has to distract them to pass through.

Half-Life: Alyx[]

In Half-Life: Alyx, juvenile tentacles can sometimes be found growing out of Xen growths in the environment. These tentacle stalks appear to be roughly two feet high, and tend to avoid the player - showing no signs of aggression. A drawing of adult tentacles can also be found.

Behavior and skills[]

In terms of behavior, Tentacles aggressively target prey in the immediate vicinity of their pits. While searching for prey, they gently tap the surrounding area, but when even the quietest noise or vibration is detected, the Tentacles will furiously and repeatedly strike at the location where noise or vibration was detected. When a Tentacle comes in contact with prey, it will attempt to pull it into the pit, presumably where it is consumed and digested. In the game, this behavior is witnessed firsthand by the player when a scientist is grabbed and taken, screaming, into the pit at the base of the Tentacles.

If unable to detect any audible source, the Tentacles appear distressed, and occasionally they appear to be groaning, even making deep, low-pitched groans at times.

In the game, the Tentacles cannot be destroyed with the player's arsenal, but shooting the stalk a few times will temporarily drive the creature into its burrow (except in Source version). Great care must be taken when moving near them, forcing the player either to silently crouch past the burrow or cause a distraction with explosives (preferably hand grenades, as this does not reveal the player's location with sound), allowing the player to sprint out of range. It is a good idea to use this tactic, as tentacles can kill the player with one or two strikes.

It should also be noted that in Blast Pit, Tentacles can hear Gordon climbing ladders.


Moan 1

Moan 2


Behind the scenes[]

  • Chuck Jones designed the Tentacle and the Silo D scene where the creature grabs the scientist and hauls him screaming from Silo D-01's control room. According to John Guthrie, no one at Valve was prepared for anything like this scene. When they saw the effect it had on gamers in sneak previews, they knew they had made the right decision to put animated sequences directly into the game rather than setting them apart in cutscenes.[3]


  • The code of the Tentacle's base is called "cycler," which is used to spawn props in GoldSrc.
  • The tentacles of the Gene Worm are similar to the Xen Tentacle.
  • It is unknown whether the Tentacles are all single-minded organisms bound to the base or if they are simply appendages controlled by the base.
  • The Tentacles will reappear if the player uses the "noclip" cheat and goes back to the silo in the chapter Blast Pit as if they were not killed.
    • However, this may not happen in the Steam version.
  • The Tentacle is only vulnerable to scripted circumstances and the console command "impulse 203".
  • The Tentacles are unaffected by the console command "Ai_Disable" which only disable nearby NPCs.
  • The "base" of the Tentacles is only seen once in Half-Life.
  • According to a Scientist, the Tentacles encountered during Blast Pit were growing out of the ground.
  • It remains unknown how Tentacles arrived on Earth.
  • Oddly enough, Tentacles can kill the player instantly in Easy mode, despite taking two hits to do so in higher difficulties.


Concept art[]





List of appearances[]


External links[]