"Earthlings have stolen valuable materials for their research. Reclaim the stolen crystals.."
— Briefing
In this bonus mission of Decay, 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 the Black Mesa and take it back to their leader Nihilanth. It is also interesting to note that the level itself is connected to the same parking garage seen near the end of Opposing Force, where the nuclear warhead is disarmed by Adrian Shephard and rearmed by the G-Man.
This Chapter contains examples of:
- Bonus Stage: In the original game, in order to unlock the Bonus mission, an A-grade was required on all nine of the other missions (although the ability to play as a Vortigaunt in the main Half-Life singleplayer campaign was also possible through a cheat code which unlocked Alien Mode). In the fanmade PC port, this mission is unlocked through a bonus puzzle in the mission "Domestic Violence".
