The engineer

Engineers are humanoid, hairless with very pale skin, through which many blood vessels are visible. Their eyes are said to be "dead seeming," with pupils shaped like oblong crosses.

Engineers stand 10.36 (3.14m) feet tall and, like humans, breathe oxygen. However they are seemingly able to withstand higher carbon dioxide concentrations than humans--they are able to breathe unassisted and unprotected on the surface of LV-223′s which has carbon dioxide concentrations that would be lethal to humans.

Engineers possess great physical strength, as demonstrated when one kills one of Peter Weyland's escorts by sending him flying across the room with a single punch Little is known about the Engineers' history, but the Engineers are shown to be the creators of the human race, visiting Earth during its primordial stage. On primordial Earth, a lone "Sacrificial Engineer" ingests an unknown substance, later revealed to be a black goo, causing his body to dissolve, which in turn seeds the planet with his DNA, hastening the evolutionary process. The Engineers continue to visit Earth to secretly observe the human race's development.

Approximately 2,000 years prior to the Prometheus expedition to LV-223, the Engineers stationed there formulated a plan to wipe out humanity, for reasons unknown, by releasing a pathogen they created for the purpose. However, later events suggest that they lose control of the pathogen leading to the deaths of all but four of the Engineers. The survivors take refuge aboard their ship, storing themselves in the vessel's Hypersleep Chambers on the vessel's bridge. However, even while this plan is being formed and executed, Engineers were still in the habit of visiting Earth, as a number of the artifacts seen at the beginning of Prometheus date from the 7th century CE.

In 2089, archaeologists Elizabeth Shaw and Charlie Holloway discovered 35,000-year-old cave paintings on the Isle of Skye on Earth depicting a tall figure pointing to a series of stars. This depiction matches similar illustrations found on artifacts from a variety of Earth cultures and time periods--cultures that did not and could not have any contact with each other. Shaw and Holloway interpret this common theme as referring to a specific set of stars within the galaxy and that their depiction in ancient Earth artifacts was the result of contact with an alien species. Shaw expresses the belief that these extra-terrestrial beings, whom she dubs "Engineers" caused the depictions to be created as an invitation for humans to make contact with them.

Shaw shares her findings with Peter Weyland, the elderly CEO of Weyland Corporation, who funds an expedition aboard the vessel Prometheus to the moon LV-223 in orbit around the star system depicted in the artifacts.

The Prometheus arrives at LV-223 in 2093, following a two-year journey. The crew explores the moon's surface where they come across an alien structure--built by the Engineers. While exploring the structure, the Prometheus crew discovers Engineer bodies, as well as several strange canisters that, unbeknownst to them, contain the Engineers' pathogen. The crew's interference with these canisters causes the pathogen to be released. This leads to a number of deaths among the crew either as a result of indigenous life mutated by the pathogen, direct mutation of members of the crew, or in attempts to deal with the fallout from those events. Meanwhile, the android David brings one of the canisters back aboard Prometheus and deliberately infects Holloway with the pathogen by spiking his drink.

The crew returns to the Engineer structure and tries to locate two missing crewmates. While doing so, the android David discovers a vessel within. He explores the ship and locates the bridge, containing the Hypersleep Chambers the Engineers had sealed themselves in. However, only one of the four has survived. David does not share his discovery with any of the crew.

Upon the crew's return to the Prometheus, David tells Shaw that she is pregnant. However, the fetus is not human, but the result of Shaw being infected by Holloway when the couple made love the night before. David then drugs Shaw with the intention of having her put her into cryosleep until the ship returns to Earth. Shaw manages to evade the crew sent to put her into cryosleep and makes her way to the medical bay. Once there, and in severe pain as the creature tries to exit her body, she performs surgery on herself. She removes a thrashing, grey, tentacled creature--a Trilobite--which the surgical equipment holds in place while she escapes the room, sealing the creature within.

Still suffering from her surgery, Shaw discovers that the elderly Peter Weyland has traveled aboard the Prometheus in secret, with the objective of '[meeting his] maker,' believing the Engineers can save him from death. David leads a party comprised of Weyland, Shaw, and two other members of the Prometheus crew to the Engineer ship, with the intention of reviving the surviving Engineer so that Weyland can converse with it.

They pass through the Engineer ship's cargo bay in which are stored thousands of canisters of pathogens. Upon reaching the bridge, David wakes the surviving Engineer and attempts to speak to him. The Engineer then turns hostile, decapitates David, and bludgeons Weyland with the head before killing the rest of the party except Shaw, who manages to escape.

The Engineer reactivates the ship and sets course for Earth, presumably to carry out the original mission of wiping out the human race. With Shaw still on the planet, the remaining crew of the Prometheus sacrifice themselves to prevent the Engineer ship's departure from LV-223, jettisoning the vessel's lifeboat for Shaw to use, before ramming the Engineer ship at full thrust, causing the alien craft to fall back to the planet.

Shaw enters the lifeboat and begins gathering supplies, when she hears thumping noises. She moves towards the noise which is coming from the medical bay she used earlier. Peering into the room, she is startled by an enormous tentacle slapping against the window from the other side--the Trilobite she removed earlier has grown to massive proportions. As she backs away, David (or rather his head) signals Shaw from the Engineer ship, warning her that she needs to leave as the Engineer is coming to find her. However, she only manages to move a few steps before the Engineer breaks into the lifeboat and pins her against the doors of the medical bay. Shaw activates the door controls releasing the Trilobite, which proceeds to ensnare the Engineer, while Shaw (just about) makes her escape.

The Engineer and Trilobite grapple with each other, the Trilobite gradually wrapping more and more of itself around the Engineer. It moves its central mass forward, flowering open to reveal a toothed maw surrounded by what look like eyes. The eyes turn out to be slender tentacles which it shoots forward and wraps around the Engineer's head, holding it in place so that the proboscis inside the maw can ram into the Engineer's mouth to begin impregnation.

Shaw returns to the Engineer's ship after David tells her of a second vessel they can use to leave LV-223. Together they activate the other ship which is last seen powering away from the planet.

Back aboard the lifeboat, the corpse of the Engineer twitches before its chest bursts open, spilling a newly born Deacon onto the floor, which stands to release its birthing cryThough not much is known about the Engineers, it is shown that the Engineers have displayed advanced forms of culture that exist within their society, such as language, visual arts, music and clothing.

The Engineers' writing system is strikingly similar to Mesopotamian cuneiform that can be found in the middle-east, and their hieroglyphs are identical to what is found in Egypt, Mesoamerica, and other places on Earth. When the android David talks to the last Engineer on LV-223 and is seemingly understood by it, he appears to be using a form of proto-Indo-European Ursprache ("original language") that was spoken by the first Indo-Europeans circa 3,000 BCE and that David has learnt on the flight there, where earlier we've seen him practicing the language with Schleicher's fable, which is written in a modern reconstruction of proto-Indo-European. While the Urheimat ("original home") of the first Indo-Europeans is still under scientific dispute, the most respected theories locate it either in the Asian or Pontic steppes (Kurgan hypothesis), near the Black Sea, or in Anatolia.

As Ridley Scott has stated that he has developed the mythology of the Alien/Prometheus universe with Erich von Däniken's book Chariot of the Gods in mind (where Däniken dwells on the possibility of the source of life, intelligence, and civilization on Earth being extraterrestrial), it is interesting to note that according to the Kurgan hypothesis, the chariot was instrumental in the belligerent spread of the Indo-European language and culture in Asia and Europe, as the first Indo-Europeans had been first to domesticate, breed, and worship the horse, which would add an interesting new aspect to the phrase Space Jockey. According to Wikipedia, the word jockey in the English language itself derives from the name John also colloquially used for boy, as cognate to the custom found in many Indo-European languages to have the same or similar words for boy or child as well as for colt, i. e. the male offspring of horses, which in turn points to the significance held by horses and chariots in early Indo-European culture.