Gordon finally arrives at the Lambda Complex, an advanced teleportation research lab where the remnants of the Lambda team have taken refuge. After fighting his way through the facility's reactor core, he learns that the satellite he launched failed to reverse the effects of the Resonance Cascade. This is because a being of immense power is holding the rift between the two worlds open. In order to close the rift, he must teleport to Xen and kill the creature himself.

Lambda Core is the fourteenth chapter of Half-Life.

The primary enemies encountered in the chapter are Vortigaunts and Alien Grunts (as the Marines have now evacuated). The player also encounters a group of Black Ops Assassins in a storage room. A puzzle element is introduced as well: The teleportation labs harbor one-way portals (each leading to various locations in the Complex, as determined by a series of numbers and ports) that the player must use to progress, as most of the paths have been blocked off.

Near the end of the level the player is given a chance to fully restock on ammunition, health, and suit power, and is introduced to the Long Jump Module.

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