- "What do you mean, "They cut the power?" How could they cut the power, man? They're animals!"
The Soldier, also referred to as the Warrior, is the Xenomorph hive's primary attack force with the primary function of protecting the Queen and the Eggs. It is fast, reasonably tough, and a savage combatant. Even in death the Soldier is dangerous, bursting apart when killed and drenching nearby enemies in acid.
After progressing through the Lurker phase, the Soldier stands at around eight feet in height and about 14-16 feet long tail included. It is black in color, with a long, segmented tail and a secondary set of jaws inside its mouth; which it can use to maim or kill prey. They are shown to possess incredible strength, enough to break down metal pressure doors and easily punch through Armored Quartz, which withstands above 160,000 pounds per square inch compressive force. Warriors can blend into the surrounding spaces in their hives as well other terrain, making them difficult to detect until they move, although other Xenomorphs can do this as well.
The most visible difference in Soldiers from other Xenomorphs is the ridged head. The head carapace is also harder than that of Lurkers, allowing them to ram into targets.
When a Xenomorph Soldier is killed by weapons that cause massive physical trauma, its pressurized bloodstream causes the creature to explode, showering the surrounding area with concentraited molecular acid. Napalm weaponry or high powered energy weapons that produce high levels of heat, if used successfully, will leave a charred mass, and will cause the acid to turn into a extremely toxic vapor that is lethal if inhaled and lethal to the ozone. Their acidic blood is capable of causing severe injury to humans, notably causing the death or injury of several colonial marines during their investigation of Hadley's Hope when they were too close a dying Soldier.
In some cases, the Soldier can evolve into a different form, which has very large blades on the top and bottom of the tail, with large blades on the elbows and calves as well. Soldiers are shown to be extremely agile; capable of navigating through vents, up walls, and navigating large areas swiftly. They also have an astonishing leaping ability.
Soldiers are fairly intelligent, but compared to the Lurker, they have a more brutish and savage approach to combat. While they were able to cut the power at Hadley's Hope and use the vents and shafts to enter the base, they charged directly into the fire of Colonial Marines indicating a lack of concern for their own personal safety.
- James Cameron stated in the Aliens commentary that Soldiers are indeed the adult form of Lurkers.
- Soldiers seem to be capable of delivering some sort of neurotoxin from their tail, as displayed in the original shooting script for Aliens and the novelization that both featured a scene in which Lieutenant Gorman is "stung" by a Soldier's barb tail and was rendered unconscious.