Runners are powerful, four-legged Xenomorphs from the Alien franchise that can occur when a Facehugger impregnates a quadrupedal animal with a Chestburster embryo. This first appears in 1992's Alien 3 when a stray Facehugger escapes Ellen Ripley's EEV ship and attacks a four-legged creature in Fiorina 161's prison complex.
As if regular Xenomorph Drones weren't fearsome enough, Runners are much faster and stronger than their standard counterparts. This gives them even more of an edge against their enemies — which includes pretty much everything outside of their Hive.
They also appear to grow much faster than your average Xenomorph. In the first Alien movie, for example, the Chestburster runs—or slithers—away to find a safe place to evolve into its larger form, which takes about an hour or two. The Runner in Alien 3, however, seemed to be almost fully grown immediately upon exiting the host.
Runner Xenomorphs begin their lives like any other Xenomorph, starting with a Facehugger hatching from an Ovomorph. It is at the Facehugger stage that the Runner Xenomorph deviates from the standard Xenomorph form. A Facehugger's main goal is to search for a host to implant a Chestburster embryo. They are not picky with their hosts, capturing almost anything as long as they live and breathe. In most cases, a Facehugger captures a two-legged human, creating the standard Drone form.
If a Facehugger captures a four-legged creature, however, it can take on some of the host's characteristics, like its quadrupedal nature, thus creating a Runner. This is thanks to a process called DNA Reflex.
DNA Reflex
DNA Reflex is a unique process that occurs during the incubation of a Chestburster. When captured by a Facehugger, it implants an embryo of sorts that uses the host's natural processes to grow and develop into a Chestburster.
This makes them more of a parasitic fetus that requires the active participation of the host to grow. As the Chestburster uses its host's body to incubate, it absorbs the body's DNA in the process. The host's DNA has a direct effect on the Xenomorph being grown and can change its form upon its 'birth'.
Runner Origins
When it comes to Runner origins in particular, they can be traced back to Alien 3, where a Facehugger sneaks off of Ripley's ship and impregnates a dog (or an ox in deleted scenes).
The specific host that is captured changes depending on what edition of the movie you are watching. In the standard edition, the Facehugger captures a large dog. In the Special Edition of Alien 3, however, the Facehugger impregnates an ox that the prisoners on Fiorina 161 were used to shift heavy cargo and perform other manual labor jobs.
On a more general note, Runners, as Xenomorphs, share the same overall origin stories as all other Xenomorph varieties. That subject is a hot debate, however, as there are three — maybe even four — Xenomorph origin stories that have been posited by different Aliens media.
The three main theories are as follows: - the Engineer-created theory (Prometheus/Alien: Covenant), the Predator-bred theory (Alien vs. Predator), and the natural evolution theory (extended universe media). It is difficult - or impossible - to say which is correct, so it’s necessary to explore them all.
Then, there is the matter of Alien: Earth. Alien: Earth is a series set to premiere on Aug, 12, 2025, so we will not know what origin story it follows or even if it creates its own until then. The only thing that is clear at this stage is that it appears not to follow the Engineer/Black Goo theory.
Xenomorph Origins According to Alien
The origins of Xenomorphs in the Alien universe follow the actions of the Engineers. The Engineers were an ancient and highly developed species that created Xenomorph-adjacent beings through a series of biological experiments involving a mysterious and highly potent Black Goo. This Black Goo acts as a mutagen, changing its host and creating new and dangerous creatures.
In the opening scene of the 2012 film Prometheus, we see an Engineer consuming the Black Goo and subsequently dissolving into a flowing river, spreading his DNA and implying that that is what planted the seeds of life on Earth that eventually culminated in humanity.
It is later revealed in the movie that although this Black Goo can be used to create life, it can also be used to destroy it. The mysterious Black Goo has unpredictable effects when exposed to certain life forms, creating biological weapons that can completely decimate civilizations. As Prometheus progresses, the humans discover urns containing Black Goo and find evidence that the Engineers were planning on using it to wipe out the human race.
This Black Goo mutagen and the Engineer’s experiments became uncontrolled, playing a pivotal role in the creation of the modern-day Xenomorph as seen on Alien’s USCSS Nostromo in 2122.
Xenomorph Types Seen in the Alien Movie Franchise
David
Alien: Covenant introduces some new theories, placing Synthetic human David in the leading role in the creation of the Xenomorph. David was trying to create the ‘perfect organism’ through more biological experimentation using the Black Goo and DNA gathered from other unsuspecting victims. The movie introduces a number of different species thanks to David, including Neomorphs and the first iteration of the Xenomorph.
It was later theorized, however, that David merely hijacked a pre-existing design created by the Engineers rather than creating it from scratch himself.
In the Alien vs. Predator universe, the Xenomorphs were a species bred and manipulated by the Predator (Yautja) species. The Yautja (or Predators) are even bigger and badder than Xenomorphs and pride themselves on their hunting prowess.
Taking down Xenomorphs is both a sport and a rite of passage for these apex warriors, who intentionally seeded planets with Xenomorphs specifically so they could hunt and kill them to challenge themselves.
Predators were revered and worshipped as Gods in the ancient world. Ancient civilizations were heavily influenced by the species, building pyramids for them and offering humans as sacrifices to the Facehuggers to create the Xenomorphs that they would subsequently hunt.
This theory trashes the idea of the Engineers altogether, making way for a whole new narrative where the Predators cultivated the Xenomorphs for the fun of sport and to challenge their abilities. This explains why the Xenomorphs are so prolific on Earth, but not how they were created in the first place. Rather than being specifically created, the species already existed but was harnessed by the Predators.
Xenomorph Origins According to Alternate Universe Media
There is one last Xenomorph origin theory to explore. This one is posited in some of the comic books and video games based in the Alien universe. Comics like Alien: Outbreak, and Alien: The Theory of Alien Propagation explore the idea that Xenomorphs evolved organically on a planet named Xenomorph Prime.
Xenomorph Prime is said to be a very inhospitable environment. This, coupled with the competition from other predator creatures on the planet, forced the species to become extremely efficient and violent in order to survive. This is what led to the Xenomorphs becoming such brilliant predators, especially when they’re placed in confined spaces filled with soft and squishy humans.
This theory removes all meddling from outside sources and explores how the species would have naturally developed on their hostile planet. In addition to being mentioned in the comics, Xenomorph Prime is also explored in concept art for things like the 2010 Alien vs. Predator video game.
It seems more likely that the Xenomorphs in Alien: Earth's universe will have evolved organically over millions of years in space. Whether that evolution took place on Xenomorph Prime or another planet is unclear, and we will have to wait for the release of Alien: Earth to know if that's even their angle at all.
We know from the trailer that a rogue ship crashes in Prodigy City, on Earth, in 2120, and the craft contains five of the most dangerous alien species in the universe, one of which is an Ovomorph.
Runner Variants
Runners are created during the DNA Reflex process, where they adopt some of the DNA of their host. If the host differs, the DNA they can absorb differs, which leads to new varieties of Runners. Different variations of Runners born from creatures like large cats or even rhinos have been speculated on but never actually appear in any Alien media.
There is, however, one particularly fearsome Runner variant that is much more powerful than the standard form. It is worth noting, however, that there is no solid confirmation that the Crusher is a Runner variant, but it is a decent guess based on our current understanding of how Xenomorphs get four legs.
Crusher
The Crusher is a unique Xenomorph that first appears in the video game Aliens: Colonial Marines. There, you have to fight a massive boss monster by the name of the Crusher. The exact origins of the Crusher and its quadrupedal nature are blurred.
What is generally understood about the birth of the Crusher is that it was possibly created from a Queen Chestburster that was exposed to radiation during its development. This caused the resulting Xenomorph to have significant mutations including improved size and strength, and possibly, its four legs.
It is also theorized that the Royal Facehugger must have impregnated a four-legged creature with the Queen Chestburster, resulting in the Crusher's four-legged stance. The host was never specifically seen, however, so it could have also been the radiation that caused the Xenomorph to walk on four legs.
Runner Appearances
Runners are rarer than their two-legged counterparts, but they still make appearances in many Aliens movies, games, and books.
Movies
Alien 3 (1992)
Games
Aliens: Colonial Marines (2013)
Aliens vs. Predator: Extinction (2003)
Aliens: Fireteam Elite (2021)
Aliens: Dark Descent (2023)
Comics & Novels
Aliens: Ice Storm
Aliens: Showdown
Aliens: Stampede
Aliens: Fireball
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