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"X-Ray Zulu, are you there? We need backup in the waste sector! Some sort of worm creature! Tower and Eddy are down and I've lost contact with the rest of the squad! We need backup now! NOW, damn it, NOW!"
―HECU Marine[src]

The Pit Worm is a Race X creature found in the Waste Processing Area 3 of Black Mesa during Opposing Force’s ninth chapter, Pit Worm's Nest, as the game's first boss.


The Pit Worm's caterpillar-like segmented body supports a head dominated by a single large eye with two vertical eyelids, and a twelve teeth mouth under it. It is found in the Waste Processing Area 3's Toxic Disposal Basin, a large room partially flooded with hazardous water, where the creature came from the ground (like an earthworm, hence its name). Its body is likely longer than seen, although it is unknown how much.

Behavior and skills[]

The Pit Worm's eye is its primary weapon, capable of firing a searing energy beam at nearby enemies and the player. If enemies get too close, the worm also has large claws to strike out with. If it is shot in the eye with most weapons, it will recoil, shielding it with its claws for a few seconds before striking aggressively at the player. The Pit Worm makes bird-like vocalizations. Like the Gene Worm, only one individual of that species is ever seen in-game.

If one manages to run into one of the many passages leading into other rooms, the Pit Worm will screech angrily and swipe viciously at the entrance of the passage taken.


Pit worm laser blood

The Pit Worm hitting Shephard with its eye laser.

Half-Life: Opposing Force[]

At the end of Opposing Force's eighth chapter, Vicarious Reality, Shephard picks up a radio transmission from a group of HECU Marines fighting the Pit Worm. In the next chapter, Pit Worm's Nest, Shephard reaches the Waste Processing Area 3 and finds all the soldiers dead (although many were likely killed by Pit Drones infesting the area), and the Pit Worm standing in the Toxic Disposal Basin. As traditional weapons only upset the creature without killing it, Shephard must use toxic waste to his advantage. To do so, he must activate the steam vent (located near the creature), the main pressure valve (also located near the creature, and to be accessed thanks to the hand-held Barnacle and Spore Launcher spores on the wall, since the ladder to access the valve is broken) and the primary pump gearbox (located in Waste Station 02, another area, and by using an emergency override button) to unlock the toxic waste arrival, then release the toxic waste with the waste flush button, flooding the room with chemical waste and eventually dissolving it. After that, Shephard merely has to activate the bridge previously blocked by the Pit Worm, and cross the Toxic Disposal Basin room to proceed further, in sewers leading to ruined hangars in Sector G.

Behind the scenes[]

  • The Pit Worm obstacle is very similar to the Tentacle puzzle in the Half-Life chapter Blast Pit. Both creatures are similar in their shape and behavior, and both reside in tall cylindrical chambers. In both instances, the player must activate multiple switches around the area before activating an ultimate sequence to kill the creature. The player can then continue, as the creatures both block the exit.
  • The valve and the gearbox to be activated are obvious references to Valve Software and Gearbox Software, left there as Easter eggs. The mention of Steam is purely a coincidence as the game platform wouldn't launch for approximately 4 years after the release of Opposing Force.
  • The Larva Crab Worm in Gearbox Software's Borderlands is quite similar in appearance, with a long, segmented body; a single, large eye; claws near the front of the body; and a ranged attack. It is likely based on the Pit Worm.


  • Pit Worm does not react to the Shock Roach, despite being irritated with any other weapon.
  • The Pit Worm is invincible and its death sequence is scripted. If spawned with the console it cannot be defeated, although the command "Impulse 203" can be used to remove it.
  • If the player enters the basin where the pit worm is inhabiting, the water will harm the player as if it was toxic. This is odd due to the fact that toxic waste is needed to kill the pit worm although it may be likely that the basin is not hazardous to the creature and only human beings. Plus, while the water before the waste is flushed reads as biohazardous on the P.C.V.'s display, the flushed waste indicates a Chemical hazard.
  • If the player enters to the waste station 2 when the pit worm is dying, but the toxic waste still has not reached the floor you are standing, the scene is paused until you enter again to the pit. However, if you enter to the waste station 2 when the floor is covered with toxic waste, once the loading screen has gone, the toxic waste will disappear, but if you enter to the pit again, Shephard will appear dead once the loading screen finishes, and the toxic waste will cover the floor again. but, if the player jump in the exact time, if the loading screen appears when Shephard is in the air, he will not die after entering the pit map, but the quickly damage per second that the toxic waste does will make it difficult to move to an area free of it (even worse if the player has no energy in his suit or health). [this section needs to be rewritten as it is pretty difficult to follow the cause and effect of various actions]
  • The pit worm will react to the player's actions by attempting to lower its body into the basin, should the player dive into it. However, the creature is unable to do fully, due to its size.
  • The player cannot enter through the hole (without noclip) that the pit worm dug up.


List of appearances[]