Ancient Martian civilization

The ancient Martian civilization was a civilization depicted in Doom 3 which was discovered by the UAC beginning in the year 2115 with the discovery of subterranean ruins at Site 1, Site 2, and Site 3 during construction of the company's first Martian underground bases. Implied to be millions if not billions of years old, these ruins contained important cultural records in the form of stone tablets as well as technological artifacts. The discovery of the Ancient Martian civilization eventually leads to the re-invention of teleportation, and an invasion by the forces of Hell, bringing about the plot of Doom 3 and its expansions.

Castes
According to the research of chief archaeologist Pierce Rogers, the ancient Martians were bipedal humanoids similar in shape and size to humans who had a highly structured society consisting of castes, including at least two, for warriors and laborers (a third unlabeled caste is depicted in Dr. Rogers' diagram of the stratification, which is likely for a priesthood considering the supernatural nature of many of the civilization's records).

Writing systems
Evidence of at least three separate writing systems is visible between the culture's various constructions and artifacts. The first appears highly mathematical in nature and seems to consist of various arrows and operator symbols - this writing system is particularly evident on the structures and tablets at Site 3. The fact that it appears mathematical might be evidence that it was designed to be free of cultural interpretation or context, and thus intended to be easily decipherable in the far future with a minimum of such information available (an idea reminiscent of the message from the system in 's science fiction novel , a message which also encodes directions on how to build an advanced transportation device).

A second writing system can be seen in the tablets from Site 1 which appear in Doom 3: Resurrection of Evil. This writing appears more runic in nature, with relatively simple characters consisting of straight strokes and some curves. The meaning of inscriptions written in this system were only fully unlocked through the use of a small cipher tablet known as the Primitive.

A third writing system, occurring only on the culture's architecture, consists of a small set of complex hieroglyphs which seem to have a one-to-one correspondence with certain words (the words "life" and "death" amongst them). Somewhat oddly, this writing system is shared with Hell and may have been co-opted, either by the demons of Hell from the ancient civilization, or vice versa (that the demons are said to have intentionally absorbed the similar runes of Argent D'Nur in Doom (2016) after having conquered it, this could form a retroactive explanation).

Oblong ovals similar to the Egyptian filled with abstract patterns of lines can also be observed in the ruins. It is unclear if these constitute writing.

Technology
Despite the fact that their records were left in the form of stone tablets, the Ancient Martians controlled a significantly advanced level of technology which far surpassed the state of the UAC even in 2145, which the UAC's scientists were only able to describe as "mystic" in nature (thus invoking the third of, which states that any sufficiently advanced technology is indistinguishable from magic).

The tablets themselves were remarkably advanced despite their primitive composition and appearance, and were stated by the UAC to have been created with a precision which even their own tools and methods could not replicate.

The highest element of technology found in the ruins was the teleporter. Located in Site 1, and beneath the eventual location of UAC's Erebus Facility, the ancient portal was dormant and could not be reactivated through any means available to the UAC scientists. Reverse engineering of this device using encoded data recovered from the stone tablets was completed in 2139 in the form of Project Mercury, the teleporter which can be found in Delta Labs - Level 2a.

Another significant technological artifact recovered from the ruins was the Soul Cube, dubbed artifact U1 by the UAC. A levitating but otherwise inert cube whose mass could not be measured, and which could not be opened, activated, or scanned in any way, the Soul Cube's purpose remained unknown to the UAC until just before the demonic invasion occurred.

Other technological marvels found in the ruins include crystalline star charts and maps which self-illuminate through some unknown means, levitating pods, and ancient but still functional automated defense turrets which activate whenever demonic presence is detected. The Site 1 ruins additionally contain many dangerous traps which still function with deadly efficiency despite their vast age - these also seem to respond to the presence of demons and are dormant until the second invasion of 2147 begins.

War with Hell
The ancient Martian civilization was destroyed in a war with Hell after their invention of a teleportation device led to the opening of a portal into the netherworld. The ancients evidently fought a protracted battle against the demons, even going so far as to take parts of Hell for their own (one being in the form of the Hell Outpost, for example).

During this battle, a key event seems to have been the discovery of the Artifact, also known as the Heart of Hell. This demonic artifact was of great importance to the demons, but its possession by the ancient Martians also put them in further jeopardy, as the Artifact itself can act as a portal to Hell. Fragments of stone tablets documented in the Phobos Labs systems display armored skeletal demons swarming from the Artifact, and also depict seemingly terrified humanoid figures being struck down by the Invulnerability Hunter, one of the three powerful demons who protect the Artifact. Unable to destroy the Artifact, the Martians instead sealed it away, inactivating its ability to be used as a portal.

It is likely that the Ancient civilization also faced the Guardian of Hell in their battles, as they left behind tablets that depict the beast.

Eventually, the tide of battle turned decisively against the ancient Martians, and they were forced to come up with a drastic solution in the form of the Soul Cube. By combining their highest technology with some sort of ritual in which the majority of their remaining population was sacrificed, they were able to combine all the souls of their race into the Soul Cube and created a weapon which could harvest the energy unleashed during death - by killing any five victims, the Soul Cube becomes capable of energizing itself and destroying the most powerful of foes while transferring their life force back to its user.

An ancient Martian known only as the Hero was able to wield the Soul Cube in battle against the demons, and with it he stemmed the tide of the horde long enough for the portals to be closed. Seemingly he did not survive, as a sarcophagus can be found in the Site 3 ruins in the Chamber of the Hero along with the principal series of four stone tablets which detail the history of the ancient Martians.

Fate
The ancient Martians' final fate was unknown. The final stone tablet in the main series seemed to indicate that the few survivors left Mars using the teleporter, leaving to destinations unknown - the tablet referenced a star chart which, at the time of the invasion, the UAC had not yet decisively identified, though this chart seems to be found in Site 3 on the roof of the Room of Stars, and displays lines which pass through the four innermost planets of the Solar System and then go beyond.

Pierce Rogers surmised that some of the ancient Martians went to Earth, where they may have become ancestors of modern man.

Before leaving Mars, the ancients created the stone tablets as warnings to any future beings who might discover their teleportation technology. Though detailing the workings of the technology, the tablets also warned firmly of the consequences of its use. Unfortunately for the UAC, the technology was understood by them long before the warnings were fully grasped.

Contact with other civilizations
While the relationship of the ancient Martians to any other races is uncertain and must remain conjectural, it seems that they had at least some form of contact with the civilization of Argent D'Nur which is depicted in Doom (2016). A record of the ancient Hero's battle against the demons using the Soul Cube was left by these people, indicating that they at least knew of its occurrence.

Due to the resemblance of the ancient Hero to the Doom Slayer (and thus also to the protagonist of the classic Doom games), some suppose that they may all in actuality be the same person, with, as the demons state in their own records, a history of fighting against Hell which spans across dimensions and across eons of time.

Ancient Martians and teleportation
The first tablet in the main series of four details the ancient Martian race itself. It displays a chart of the Solar system similar to the one found in the Room of Stars and a humanoid figure below it. At the bottom, an image of a teleportation device can be found. Narratives created by Pierce Rogers indicate that this tablet was the one which spelled out the principles behind teleportation and led to the reverse engineering of the Erebus device by the UAC.

Demonic invasion
The second tablet details the demonic invasion and the war with Hell. It displays figures of an imp and a Hell knight below an image of an unknown skull-like entity. It also displays another picture of the teleportation device, this time with a black essence seeming to explode from it with tentacle-like growths.

The Soul Cube
The third main-series tablet details the creation of the Soul Cube and the required sacrifice of the ancient Martians. A cube at the top of the tablet is followed by distorted figures of ancient Martians who seem to be flowing into it as it radiates energy.

The Hero
The fourth and final tablet of the main series depicts the ancient Martian Hero and his battle against the demons using the Soul Cube. All existing copies of this tablet were badly damaged and so it was the least understood by the UAC. Notably, the Hero's face cannot be seen in any of them. This tablet forms an allusion to the original Doom box art as illustrated by Don Ivan Punchatz.

Guardian tablet
Several copies exist of a tablet which depicts the Guardian of Hell. Nothing else is learned about its contents in the course of the game.

Hell Hunter tablets
A series of three tablets were created which detailed the Hell Hunters and their abilities, along with a detailed depiction of the Artifact.

The Primitive
The Primitive is a small tablet which depicts the Artifact and acts as a cipher key for the other Site 1 tablets. Failure to understand the purpose of the Primitive led to the second invasion in 2147 under the administration of Dr. Elizabeth McNeil after discovery of the Artifact by a team of marines in the ruins beneath the Erebus facility.

Unknown small tablets
Two copies of a tablet of unknown purpose can be found on display in the Phobos Labs facility. What it depicts is unknown as it is never mentioned or displayed in-game. An equally mysterious sword-like artifact on display nearby triggers a momentary psychic vision when it is approached by the marine.

Phobos shards
The Phobos computer systems contain documentation on tablet shards which detail the full record of the ancient civilization's discovery of the Artifact and the consequences of their having seized it from Hell. Among these shards are one which depicts the Artifact seemingly integrated with the gateway to what is later the Maledict's domain in Hell, skeletal demons pouring out of the Artifact, the Artifact sealed by the Martians into a protective enclosure, and the Invulnerability Hunter attacking Martians.