The room itself has been fitted with mounted weapons which are powered by Xen energy crystals. The Gene Worm is found deep underground in a seemingly abandoned industrial area of Black Mesa and appears through a portal opening powered by Sprites in a room there, apparently either unwilling or unable to fully enter this world, most likely because of the minuscule size of the portal behind it in proportion to the Gene Worm's presumably immense size and length. When the creature is idle and no threat is visible, it will gently sway its tentacles around, and emit soft hissing and groaning noises. When the Gene Worm 'dies', it sinks back into its portal, but not before emitting a ' portal storm' into the room, similar to the one that occurred as the Nihilanth died. The worm's weakness is by firing any gun at the rear of this stomach cavity It should be noted that the portal orb itself is not vulnerable to attacks. This causes it to summon reinforcements by opening its abdominal cavity to reveal a portal orb that a Shock Trooper will teleport through. Its outer hide is impervious to damage in order to kill it, the player must blind the creature by shooting both its eyes with the mounted laser guns on either side of the worm. The Gene Worm attacks with its tentacles and ejects a deadly chemical stream from its mouth. Physically, the creature resembles a green, worm-like creature with many tentacles and a beak-like protrusion similar in both shape and position to that of the Xen Tentacle.

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