Half-Life: Decay // Bonus Bölüm: Xen Saldırısı

This is the bonus chapter of Half-Life: Decay. In it, two Vortigaunts named "Drone Subjects" X-8973 and R-4913 must retrieve the crystal sample which was used in tests (and stolen by the G-Man) in Black Mesa and take it back to their leader Nihilanth. It is also interesting to note that the level itself is connected to the parking garage as seen near the end of Half-Life: Opposing Force where the Nuclear warhead is disarmed by Adrian Shephard and rearmed by the G-Man.