In the mission, the Nihilanth has assigned R-4913 and X-8973 to retrieve the crystals stolen from Xen by the Black Mesa Science Team (although it is later revealed that the crystals were actually stolen by the G-Man). Both Vortigaunts are able to regain health by damaging objects or enemies, supporting the theory that Vortigaunts can drain lifeforce/energy with their beam attacks.
- In the unofficial PC port, both Vortigaunts appear with a crowbar when looked at by the other player, while they both use only their claws and electrical attack, as any Vortigaunt. This is likely an unintended glitch.
- In both versions of the game, the words "Valve" and "R-4913" are found in an air duct written all over the walls in the mission Code Green. These words are also found in a vent towards the end of Half-Life: Uplink.
List of appearances
|Creatures||Alien Aircraft • Alien Controller • Alien Grunt • Armored Headcrab • Barnacle • Boid • Bullsquid • Chumtoad • Fast Headcrab • Gargantua• Gonarch • Headcrab • Houndeye • Ichthyosaur • Leech • Lightning Dog • Nihilanth • Poison Headcrab • Protozoan • Snark • Standard Headcrab • Tentacle • Vortigaunt • Zombie|
|Flora and minerals||Crystal • Fungus • Healing Pool • Light Stalk • Trampoline • Tree|
|Weapons||Black Hole Gun (cut) • Ceiling Turret • Grenade • Hivehand • Sentry Cannon • Snark • Snark Mine|
|Technology||Healing Shower • Thumper|
|Creatures (cut)||Archer • Charger • Fast Walker • Flocking Floater • Kingpin • Mr. Friendly • Panther Eye • Prrobot • Sand Barnacle • Snapbug • Sphere • Stukabat • Unidentified Quiver Creature|