The Old Ones were an ancient, space-faring race who had an advanced civilization before the development of the Young Races in the current age. They are notable for being the first of all the galaxy’s sentient life as well as being the first race to cross the sea of stars, making them the oldest space-faring species in the galaxy.
The Old Ones are said to have had a slow, cold-blooded wisdom, studying the stars and raising astrology and astronomy to an arcane science. It was their understanding of the universe that allowed them to manipulate alternate dimensions, and it was known that they undertook great works of psychic engineering.
As the Old Ones passed through the cosmos, a number of younger and fiercer races developed within their wake, including the Necrontyr, who struggled in their colonization of other worlds. During this encounter, the ultra-intelligent races of mystics known as the Old Ones were seen to have swiftly colonized other worlds with far greater ease and had an immense longevity to the point of immortality.
Few outside the race of the Aeldari and the Necrons know of this ancient story. Some in the Inquisition pursue the study of these ancient ones. A very few have learned of the Dreamlands, where the Old Ones may yet dwell. Those that learn too much fall into raving madness.
The nature of the Dreamlands in relation to the Immaterium is a matter of debate within the community that pursues such esoterica. The race sometime called The Great Old Ones may or may not be related to those of Aeldari myth. They are to be distinguished from the more cosmically placed entities such as Azathoth, Nyarlathotep and Yog-Sothoth, and from races such as the Chthonians, the Deep Ones, the Elder Things and the Mi-go.
Very few people dispute that Azathoth and Yog-Sothoth are Outer Gods instead of Great Old Ones, although some accounts make them ancestors of a few Great Old Ones. This has led to the theory that “Great Old One” is the term for everything younger than Cthulhu and Tsathoggua, and “Other God” or “Outer God” to be everything older.
Doubtless, the Emperor struggled with these beings when the chaos realm was forming. It remains to be seen if these beings are aspects of the chaos gods, or something far older and fouler. From the Lovecraft Wiki—TheGaffer
The Corvus Cluster is a Warhammer 40K blog documenting our gaming adventures in the fantastical sci-fi universe of Games Workshop with crossovers to the mythos of HP Lovecraft, Andrzej Sapkowski’s The Witcher, and Frostgrave.