Old One (Warhammer 40,000)

The Old Ones were an ancient reptilian race of extremely powerful Psykers considered the oldest sapient species in the Milky Way Galaxy.

History
The Old Ones are believed to be the first sapient species to have existed in the galaxy, although some sources have suggested they were a group of different but equally as powerful and ancient races. The Old Ones were extremely potent Psykers, likely due in part to the calmness of the Realm of Souls during their reign, and were also responsible for creating the Webway Network and even numerous other species through their mastery of genetic engineering, including the Laer, the Hrud, the Jokaero and the Krorks. Additionally, the Old Ones also uplifted a variety of naturally-evolved species such as the Eldar and presumably the Necrontyr. Eventually, the Old Ones advanced evolution and immense psychic power caused them to become beings of sapient energy, prompting them to reside within the Realm of Souls.

The War in Heaven
At some point, the Necrontyr declared war on the Old Ones in an attempt to unify their people against a common enemy, as well as a collective resentment for the Old Ones dismissing them to short but painful lives bought on by excessive solar radiation saturating their homeworld. The opening stages of this so-called War in Heaven initially saw the Necrontyr easily beaten by the Old Ones, until the former encountered the C'tan, worshipped them as gods and constructed physical forms for them out of living metal. The C'tan offered the Necrontyr power and immortality in exchange for their service. The Necrontyr agreed, but discovered too late that the C'tan had deceived them. In what became known as the Biotransference, the Necrontyr's souls were consumed by the C'tan and their bodies were transformed into mindless robotic slaves now known as Necrons. Without souls to connect them to the Warp, the Necrons and their C'tan masters proved immune to the Old Ones psychic powers, slaughtering the vast majority of them and exterminating most of their allied races. The Old Ones suffered even greater losses when their desperate misuse of their psychic powers enabled the Enslavers to enter the material universe and join the conflict.

Despite all odds, the War in Heaven ended with the C'tan defeated. The Eldar, having acquired access to the Webway, invented Wraithbone and used it to construct robots controlled by the souls of their dead, such as Wraithguard and Wraithlords among others, capable of countering the Necrons' onslaught. Additionally, the Silent King of the Necrons regained self-awareness and realised what he and his people had been turned into. Once the tide turned against the C'tan, the Silent King turned the Necrons against the C'tan and destroyed them, enslaving their shattered remains.

Legacy
The Old Ones are now considered extinct as of the War in Heaven. Some sources state they were wiped out by the C'tan and Necrons, while others argued that some survived the war, but were destroyed afterwards when the extreme imbalance of life and death in the galaxy, as well as the mental devastation wrought on the galaxy's remaining populations, corrupted the Realm of Souls and turned it into the Warp, resulting in the remaining Old Ones being killed by the original Daemons. After the war's conclusion, the Necrons, fearing reprisal for their servitude to the C'tan, retreated to their subterranean tombs and entered stasis for eons, waiting for the universe to forget them so they could rebuild their empire later. The Krorks, through constant fighting amongst themselves and others, gradually regressed into what are now known as the Orks, whilst the Eldar established a galaxy-spanning empire.

Some sources suggest the Old Ones may not be extinct, but are simply in hiding. The Eldar gods are suggested by some to be Old Ones themselves, although they are likely to have been inspired by them instead. Hrud mythology suggests that at least one Old One survived and promised to return from hiding if the Hrud would unite against the C'tan again. An Eldar Farseer, Eldrad Ulthuan, has also claimed to have foreseen the return of the 'old masters.' Humorously, folk-tales among the Orks suggest that the Old Ones (or 'Brain Boyz' as the Orks call them), survived the War in Heaven but gradually regressed into the Ork subspecies known as Snotlings.

On observation of an ancient tablet illustrating some of the species the Old Ones were involved with, including the Eldar and Orks, one could notice what appears to be a stylised illustration of a six-limbed creature adorned in what appears to be a carapace. This has lead some to theorise that the old Ones may have encountered, influenced or even created the Tyranids. However, no official sources have supported this theory, especially in consideration of the Tyranids' extragalactic origin.