The Praetomorph,[1] also known as the Planet 4 Xenomorph and the Stalker, was a Xenomorph variant that attacked the crew of the USCSS Covenant. The species originated on a remote planet as a result of genetic experimentation carried out by David 8.


The Praetomorph was created by the android David 8's experiments using the Chemical A0-3959X.91 – 15 pathogen as a catalyst on tissue samples harvested from Elizabeth Shaw, deceased Engineers, and Neomorphs spawned from the native species of Planet 4. Over the course of a decade, David continued to perfect his designs until he created the first Ovomorphs, which contained Praeto-Facehuggers that implanted two members of the Covenant's crew, who later birthed the first Praetomorphs. After hijacking the USCSS Covenant, David transmitted the records of his experiments to the Weyland-Yutani Corporation, expressing the intent of continuing his experiments using the settlers and surviving crew and experimenting further to create a Queen.


After Covenant captain Oram shot down a Neomorph, an enraged David tricked the former into following him to his workshop where he had been experimenting on the pathogen. David brought the captain further down, revealing a chamber filled with large eggs. Oram was unaware of how they functioned until it was too late, as a Praeto-Facehugger leapt out of one and latched itself onto his face. Sometime later, Oram awakened and had a brief discussion with David about their beliefs, when a Praetomorph Imp suddenly ripped its way out of Oram's chest, killing him.

Sergeant Lopé and Cole discovered the workshop in search of Oram. Cole found Oram's body, as well as another Praeto-Facehugger which ambushed them. During the ensuing chaos, the Praeto-Facehugger attacked Lopé and latched onto him. Cole used a knife to cut it off, with the resulting acidic blood burning Lopé's cheek. As Cole bandaged the wound, Lopé noticed an adult Praetomorph watching them from an overhead vent. Panicked, Lopé got up and fled. The alien then lunged on Cole and killed him.

The first Praetomorph attacking the USCSS Covenant's Cargo Lifter

The Praetomorph pursued the crew of the Covenant and discovered them attempting to escape on its cargo lifter. Although it managed to get aboard and endured some serious injuries, it was duly defeated by chief terraformist Daniels.

The crew took Lopé to the medical ward on the Covenant. Subsequently, ship computer MU-TH-UR contacted Daniels and informed her of an unidentified lifeform present on the ship. Daniels and pilot Tennessee headed to the medical ward and found Lopé dead with his chest burst open; the Praeto-Facehugger from earlier had managed to impregnate him.

The already-mature Praetomorph roamed the ship and ambushed Ricks and Upworth while they showered together, killing them both. Following this, the creature was lured to the Terraforming Bay by Daniels and Tennessee, where they trapped it inside one of the Terraforming Trucks and attempted to eject it. However, the truck's deployment winch was jammed by a JCB skid-steer that broke loose of its moorings, and Daniels had Tennessee release a second truck to remove the blockage. Given time to escape, the Praetomorph broke out of the truck and attempted to return to the ship, when the second truck impaled the alien and sent it flying out of the Covenant to its death.

Characteristics and traits

While virtually identical to Xenomorph XX121, this version possessed subtle differences that set it apart from its mainstream counterpart. Notably, it lacked any biomechanical features and its limbs were longer, thinner and skinless, with exposed muscles and blood vessels and gaps appearing in its armpits. Furthermore, the teeth of a Praetomorph were made of translucent bone rather than metal as seen in mainline Xenomorphs. However, they were considered more powerful and resilient than standard Xenomorphs, albeit less intelligent.[2] The shoulders and dorsal spines were noticeably different, being smaller and narrower. The Praetomorph also had a thinner, sleeker tail ending in a small barb.

This variant's egg is slightly different in overall shape
The opening and organic insides are also notably different.

The differences in the Stalker also extended to its Imp form, as well as the Facehugger to a lesser extent. Other than these differences, the Praetomorph greatly resembled a typical Xenomorph.

Like the Xenomorph XX121, the Praetomorph possessed an inner pharyngeal jaw. This appendage was capable of shooting from their mouth like a piston, with sufficient power to smash through bone and metal.[3][4]

Overall, its growth rate was incredibly fast, as it could be seen visibly growing after only just emerging from its host. Not long after this, it was next seen as a fully mature adult.

The Praetomorph could see almost as clearly and detailed as humans, albeit with "floaters" throughout its vision.


The Praetomorph was less intelligent than other Xenomorphs, and was considered more animalistic and aggressive.[5] This was exemplified during an attack on the Covenant crew; the Pratomorph in question attacked the crane claw on the ship's cargo lifter by jumping into it, which resulted in the creature being crushed to death. A second Praetomorph also attacked a camera monitoring its whereabouts, and its haste to kill Daniels led to it being trapped in a truck; though it managed to escape, another frenzied rush at Daniels led it into the path of a second truck which ejected it from the Covenant.

Praetomorphs were not friendly towards their Xenomorph cousins, much less any other species they encountered; they would attack anything on sight.[6]

Life Cycle

See: Xenomorph life cycle


Main article: Ovomorph (Planet 4)

Like all members of the species Xenomorph XX121, the Praetomorph had a complex and parasitical life-cycle that required a host. The process itself was identical to that of a standard Xenomorph, with the creature having its beginnings in an egg, though this egg was notably different in shape.


Main article: Praeto-Facehugger

Once the egg opened, a Praeto-Facehugger would emerge and attach itself to the face of a host, immediately implanting their mutagenic payload (Plagiarus linesteres). Seemingly, even a brief moment of contact was enough to ensure impregnation. Though the removal of the Praeto-Facehugger was less difficult compared to their mainstream counterpart, as it had less potent acid blood, the Praeto-Facehugger was able to offset these drawbacks by being able to implant a host within seconds of attachment. It was, however, less dexterous than a typical Facehugger.


The resultant Chestburster, classified as an 'Imp',[7] used its shape to burst its way out of its host. Once it emerged, it would undergo an almost immediate transformation. Due to this species' accelerated growth, the Imp seemed to be born almost fully developed with arms, legs, and a distinctive head.


The Imp eventually matured into a fully grown adult, known as a 'Stalker'.[8] The Stalker was presumed to be an evolutionary dead end for the species, as no further castes beyond this stage were ever recorded.[9]


  • The name Praetomorph was developed by the creators of Alien: The Roleplaying Game from the term "Protomorph" (previously used during the conceptual stage for the Deacon in Prometheus[10]) combined with the prefix "prae", taken from the Plagiarus praepotens mutagen described in the novel Alien: The Cold Forge.
  • According to Ridley Scott's director's commentary, the Praetomorph is able to regenerate from would-be fatal injuries like being crushed and dismembered, making it virtually indestructible.
  • Its design was based on that of an écorché, while its movements were based on those of a praying mantis and a baboon.[11][12]
  • The Praetomorph has a human skull underneath its smooth dome, something the original Xenomorph (from Alien) also featured.
  • The exact origins and nature of the Praetomorph have been widely debated amongst fans, with some believing David is responsible for the Xenomorph XX121 species, while others believe he merely recreated something that the Engineers created. The reason for this debate is due to evidence of the existence of a Xenomorph-like species, depicted in a mural shown inside the Engineer Ship explored by the Prometheus crew. It is still unclear if David saw the mural due to the fact that in the film it is never specified, therefore creating a debate between some fans on whether this had any influence in David's experiments or not.
    • In addition to the belief that David is responsible, some fans have nicknamed the Covenant variant a Protomorph, believing that it is the precursor or progenitor to the original species.
    • In the novelization and early drafts of the script, the Xenomorph XX121 species was created by the Engineers, and David's Praetomorph variant was created in an attempt to replicate them. The final film lacks this revelation, with Ridley Scott elaborating that late in development he had decided to have David be the sole creator of the Xenomorphs, motivated by hubris and genocidal disdain for both humans and the Engineers, with the Praetomorphs being an intermediary stage between the Neomorphs and the Xenomorphs seen elsewhere in the series.[13][14][15][16] This is supported by the Advent short film, in which David documents some of his experiments with the Chemical A0-3959X.91 – 15 pathogen and expresses the intent to use the Covenant's colonists as test subjects to perfect his creation. However, other official material such as Alien: The Roleplaying Game have disregarded Scott's statements and gone with the explanation that the Engineers had created the Xenomorphs and the Praetomorphs were the result of David attempting to replicate them.
  • In the novelization, the Xenomorph is described as possessing a biomechanical mesoskeleton, but in the film itself, the Praetomorph lacks biomechanical features, stated in interviews to have been a deliberate design decision to indicate that the Praetomorphs are intermediary between the Neomorphs and Xenomorphs.
  • The Planet 4 variant appears to have a similar life-cycle speed to those in Alien vs. Predator. It also appears that the parasite stage is capable of implanting a host within seconds of attachment. Both have caused criticism amongst fans.
  • The Praetomorph's motion capture was provided by Javier Botet, a Spanish actor with Marfan Syndrome who is mostly known for his roles in REC (2007) and Mama (2013).[17]
  • There are notable differences between the film Praetomorph and the NECA figure: the NECA figure has shoulder tubes and the tubes on the back of the figure are more upright. The film Praetomorph lacks shoulder tubes and the back tubes are more separated and bent over. That's because NECA has been provided with concept art by Colin Shulver.
  • One of the Minimates figures of the Praetomorph is named the "Goran Xenomorph", this is a reference to the actor who portrayed the Praetomorph, Goran D. Kleut.




Concept art