Primal (aka The Primal or Primal Energy) is a sort of manifestation of energy that's connected directly to The City itself. It can be likened to the life essence of The City that includes energy from every living and non-living thing in it, being described as "a pervasive field of energy that exists in every stone of The City, every lungful of air". It is also said that it could be tapped as a raw energy supply to power different mechanical mechanisms but how true this is can't be known.
Only those attuned to its presence can sense Primal energy (how one becomes or is attuned to it is never really explained fully) though these once included the Keepers, an order that was as ancient as The City itself. The Keepers used the energy to power their magical glyphs that aided them in secretly controlling The City. They were however founded on being very strict and methodical about never abusing the power and maintaining balance in the world.
During the Dark Age (sometime between BRy436 and BRy459), which was called into existence by the legendary Master Sneak Thief (old Garrett), all contact with the Primal was cut off and all Keeper prophecy, every glyph, and every bit of Keeper magic was rendered useless. This sudden shift caused a period of fear and uncertainty which was known after as the Dark Age.
3 centuries later (sometime around NRy772) the Northcrests primarily under Samias Northcrest re-discovered Primal energy and how to access it, after this point the Northcrests became the sole authority on the Primal. Samias, however, was killed in battle before he could do much experimentation with it. Samias' son Harland Northcrest didn't do much work with Primal energy either, his son Baron Elias Northcrest however chose to pursue it and spent much time studying and experimenting with it. The Baron hoped to harness it to bring about a new golden age and abolish the old gods for good.
- The balance has shifted since Erin absorbed the Primal.
- The failed ritual performed by The Awakened to channel the Primal energy along with The Baron's callous experimentation on Erin as the Primal's host had the unintended effect of releasing Primal energy back into the world again, although in a contaminated form. This also re-activated some forms of Keeper magic and technology.
- Primal energy has become tainted and exposure to primal energy is equivalent to poisoning. It causes extreme effects to the mind and body, prematurely aging and warping them, with enough exposure it can even mutate an individual into a Freak.
- Primal exposure also causes sterility in some cases; Baron Elias Northcrest was lucky enough to be one such case.
- Primal poisoning gained by exposure to Primal energy is the source of the gloom.
- The Primal Stone was locked away in the Great Safe high above The City by The Baron to try and mitigate its contaminating effects on the populace; they also tried to do this with Erin by locking her in the lowest level of Moira Asylum.
- The Primal may have been the power source behind the magic of the old gods, possibly even all magic in the Thief universe.