Films: Alien (1979), Aliens (1986), Alien 3 (1992), Alien: Resurrection (1997), Alien vs. Predator (2004), Aliens vs. Predator: Requiem (2007), Alien Covenant (2017)
Alias: Xenomorph XX121, Internecivus Raptus, Runner Alien, the Hybrid, Predalien, Neomorphs
Location: Eldritch location/Haunted home/Tundra/Civilized area
Height/Weight: For a normal one, at least 7 feet and 180 kilograms.
Affiliation: Neutral, leaning on Evil
Summary: This is it. The most infamous and terrifying thing to plague the galaxies. The deadliest threat to any ecosystem. It's not as calculating and unstoppable as the Pods, but its presence sends shockwaves of fear across any planet they happen to be on. They are the Xenomorph collective, and they will kill every last one of you.
History: The true origin of the Xenomorphs remains enigmatic, but theories abound. The most prevailing one is that they began as little more than goo. A black goo created by "the Engineers", the true precursors of man. The Engineers eventually abandoned this goo, which mutated average creatures in spore-bred Necromorphs and had the terrifying potential to implant embryos deep within the body of vicious monsters. Alas, in the distant future, an android named David would come across this substance, and when he found humans (really STUPID humans, at that) to test it on, he found that using man as a host would give rise to the one thing that could surpass us: the true Xenomorph. And pretty soon, the galaxy was crawling with Xenomorph colonies, all seeing no other purpose than to breed, kill, spread, repeat. Man was not the only race to combat them, though. The Yautja race saw them as vile scourge, and hunted them for sport and glory. And then, there were subspecies like the dog-bred Runner, that strangely tragic hybrid from the fourth film, and the goddamn malignant Predalien.
Notable Kills: They reproduce by fertilizing sperm in you, and let the baby burst out of your chest in a shower of blood and guts. What else needs to be said?
Final Fate: You can bet that there are still Xenomorphs out there, despite the scores of them dead at the hands of headstrong humans and Yautja alike. They’ve simply spread too much for extinction to be within the realm of possibility. The one silver lining is that they haven't reached Earth, and when they did, that was taken care of rather quickly.
Powers/Abilities: Perhaps most astounding of all is their ability to adapt to different hosts. Depending on the host, the physical appearance and capability of a Xenomorph will come in a variety of shapes and sizes. All Xenomorph variants have acidic blood, a spear tail, and a secondary jaw for cracking heads.
Weakness: Anything conventional.
Scariness Factor: 5-THIS. SPECIES. WAS SPECIFICALLY. MEANT TO BE. UN-F*CKING-STOPPABLE AS A WHOLE. Everything about them serves no purpose other than to destroy, divide, and conquer. They are masters of stealth and brutality all at once. If you aren't afraid of these things in any capacity, then we recommend that you seek professional help immediately.
Trivia: -"Xenomorph" comes from the Greek terms for "strange" and "form", respectively.
-Xenomorphs didn't just meet the Yautjas. They have also crossed over with Batman, the Terminator, Star Trek, Judge Dredd, Witchblade (?!), and even Vampirella. This is all mostly in comics, of course.