During the End War, allied commanders gathered the crystals after the forces of Amon destabilized the planet in an attempt to reactivate the planet's environmental stabilizer. The commanders were successful in retrieving twenty of the crystals, reactivating the stabilizer and preventing the planet's destruction.
Xenon crystals are the goal of the Co-op Missions map "The Vermillion Problem," where players are tasked with retrieving 20 of the crystals and bringing them to an environmental stabilizer before time expires. The crystals appear on the map with each lava surge, starting close to the players' bases and slowly appearing further out.
Xenon is a real-world element that exists as a gas at room temperature.