Long before the Black Mesa Incident, the Vortigaunts' homeworld was invaded by the Combine, forcing the survivors of the invasion to flee to Xen. When the Black Mesa Incident occurred, their master, a being known as the Nihilanth, viewed the rift that opened as a chance to escape, and directed the Vortigaunts to invade Earth.
Following the death of the Nihilanth, the Vortigaunts have chosen to ally themselves with the human-led Resistance in its bid to overthrow the Combine rule of Earth.
- Technically the Vortigaunts weren't really villains during the events of Half-Life as they were under the rule of Nihilanth. When first entering in the Xen factory in the final chapters of the game, the Vortigaunts don't attack the player (unless they are provoked). When the Alien Controllers are present, the Vortigaunts attack.
- An idea for the conclusion of Half-Life was for Gordon Freeman to earn the Vortigaunt's trust, and they would help lead a revolution against Nihilanth. Although this was cut, elements of his plot was carried onto Half-Life 2 with the Vortigaunts helping the human race fight against the Combine.
- Despite being allies in Half-Life 2, some Resistance members will reveal that they still don't trust the Vortigaunts.
- A character known as the 'All Knowing Vortigaunt' appears as an Easter Egg in the Water Hazard chapter of Half-Life 2. He will reveal that the Vortigaunts don't hold a grudge towards Freeman for killing their members in the original Half-Life as he had freed them.
- Enemy Vortigaunts appear in the Half-Life remake mod Black Mesa. They use the same models as the Vortigaunts from the Half-Life 2 games (with slight modifications). These versions are less hunched and have shinier smoother skin.
- A mod for Half-Life called Point of View has the protagonist a Vortigaunt and their perspective during the Black Mesa Incident.
- In the PS2 version of Half-Life there is a cheat known as 'Alien Mode' which allows the player to play a Vortigaunt during the campaign ending on the first Xen chapter. All other characters told in a garbled voice.
- In a coop campaign for the PS2 game Half-Life: Decay if the player(s) finish all levels on an A level, they unlock a bonus mission in which they play two Vortigaunts who have to retrieve an alien sample stolen by the Black Mesa Research Team.