|"Seems [Mother] has intercepted a transmission of unknown origin."
Empress Xenomorphs are apparently rare. Their physiology has been seen to differ, with some appearing similar to typical Queens (albeit considerably larger), while others have been seen to have unique traits. These include significantly tougher exoskeletal armor compared to other Xenomorphs. Empresses have been seen to possess an ability to summon lesser castes of Xenomorph to their aid, similar to Praetorians, as well as driving all adult aliens around them into a combat frenzy, causing them to be more dangerous than usual.
An Empress can arise through the evolution of existing Queens. It's possible this evolution is linked to age; the Matriarch was a very old Xenomorph monarch and looks markedly different to common Queens. In particular, her crest was more elaborate than the crest typically found on a younger Queen. Furthermore, the Matriarch was immune to simple gunfire, and the Rookie was forced to find alternative ways to kill her when he encountered the Xenomorph in her Hive, indicating a reinforced exoskeleton. Other known queens were not immune to gunfire in such a way where they could block bullets with the exoskeleton on their arms.
It has been theorized that when a planet becomes sufficiently infested with Xenomorphs, several Queens are likely to occur. Similar to ants, these Queens may all be a part of the same Hive but, instead of having equal "say" in Hive matters, will defer to an Empress. The Empress is said to win her place in a great melee, not unlike larval Queens. The Queen who dominates in this melee, either by killing or besting her sisters, thus becomes the supreme ruler of that hive.
- A very large Xenomorph appears in Aliens: Infestation. What caste it is is never revealed. A Queen, much smaller, appears earlier in the game, meaning it isn't one. It is very similar to the MUGEN Empress.
- Aliens Online
- Aliens versus Predator 2
- Aliens versus Predator: Extinction
- Aliens: Infestation (possibly)