There are other places, other planes of existence and other dimensions, beyond our own, and some of the borders between them are guarded by screaming, unknowable horrors.
Though they appear in swarms, Anattā are so rare as to be legend even to those who spend their lives immersed in legend, and are almost always only found on the bleeding edges where the everyday and the impossible are juxtaposed unbidden and unplanned. They act, if their nature can be described as wilful rather than reactive, not quite as guards but almost as… antibodies might be the closest word, violently resisting and reacting against the passage or the attempted passage of people and objects between separate planes. Most of those who have seen these creatures have, understandably, kept their distance, but all those known to have chanced crossing between worlds through the paths and passageways that they guard have been destroyed.
There is speculation that their appearance inspired the classical conception of the grim reaper, having been made more sensible to the minds of mortals, or the converse; that their form is by some strange design a more twisted and terrifying tatterdemalion reimagining of that same image. Their skulls appear ancient, pitted by weather and pocked by the imprecise alchemy of petrification and might once have been human (or something uncannily similar) but in their thick jaws the teeth, of which there are three or four emergent rows, have been filed down to needle points. If that were all, the Anattā might appear to be nothing more than that: a haunting artefact of some unfortunate mutation whose appearance would have struck an even more threatening chord for a civilisation whose belief in monsters was stronger and more certain than an understanding of science might ever be.
The concrete physicality of the skull - whose empty-socketed gaze darts constantly from side to side as its teeth snap open and shut with a bony clattering, macerating the air as if consuming all the information contained in its various scents, sounds and ethereal miasmas - is set in stark contrast to the gouts of oily-looking smoke that flow outward from the base of the skull into ragged trails in a languorous, never-ending ooze. How these two elements are fused, how they interact with one another, none has been able to suggest a sensible solution (though perhaps none could exist to explain the workings of a creature so able to rob an investigator of their senses?), but I have heard of people offering a more poetic interpretation: That the duelling duality in the nature of their physiology represents both the physical realms we usually inhabit and the metaphysical or mystical planes they stand at the gates of.
In motion Anattā pass through the air like jellyfish or squid floating through water; darting staccato between stillnesses that appear almost as serene as they are menacing. Their skulls drag the wafting, billowing tendrils of smoke about behind them, and these plumes and trails fall and spread out like a worn and tattered, rough-edged cloak, its tail ends twisting and splitting away before they touch the ground. These roiling smoke spirals linger only for a few moments before dissipating leaving no trace in air but capable of precipitating a thin, tacky film of ash and tar on anything more substantial. Even more unsettling, if you are close enough to one you can hear that the smoke that constitutes an Anattā’s body is made of whispers, whispers describing horrific torments and begging for release. These ominous mutterings are nothing so innocuous as the words of the Anattā themselves though: the creatures are living, hellish prisons.
Animated by and infused with the essences of those they have consumed, even the pain of death by their snapping, gouging jaws could barely be considered suffering compared to what awaits, becoming another voice in the dull choral roar of pleading, of begging for the relief of a second, impossible death. They attack in droves, setting upon any who dare to cross into the hinterlands which they stalk. Entangling and ensnaring their prey in the smoke of their bodies, the Anattā use their teeth to slash and rend through the skin of their victims’ chests. Their victims, so captured and with the wounds raggedly scything through to the seat of their essence, are then so utterly drained of vitality that their remains are reduced to desiccated husks. The effect is an appearance of absolute and perfect mummification, a process that should take years being completed in a matter of seconds.
Very occasionally someone comes across an Anattā that has been trapped and imprisoned - though the secrets of the method and means by which someone might come to be able to do this escape me entirely - either to be used as a particularly cruel method of execution or as fearsome guard for some priceless rarity. In such circumstances I am told that they seem almost lost, their natural menace and fearsome demeanour still apparent but absent the acute ferocity lent to them by their purpose. Without their usual confinement to the breaches between realities they wander aimlessly about the limits of their new territory. Their ability to hunt is also dulled somewhat without others of their kind; though they attack with undeniable aggression they are easily distracted by other potential targets and quick to give up the chase. Nonetheless their appearance and reputation, and the fear of being consumed and trapped in a palpable and provable nightmare for as long as that Anattā exists, mean that only the desperate or ignorant would ever knowingly risk an encounter with them.
I myself have only seen them once: a fortunately brief encounter in Aden, Yemen, near the Cisterns of Tawila. I went there to investigate a case of Delirium Tempus - on which condition I have already expounded at some length - but discovered instead that the cause of the sufferer’s malady was their proximity to a more remarkable and nefarious incident. Someone (the specific whos and hows and whys were obscured by the calamitous outcome and the distant origin of the events) had set in motion a series of relatively minor incidents and occurrences that culminated in a jagged tear being opened between our now and a possible future. I was there when the tear formed and saw, for a brief moment, what is forced to stand alongside what could be. Then the Anattā, which I recognised from accounts uncovered in my studies and investigations, swarmed in and around the tear. The sight spurred me to take flight, even while my mind was trying to record as many details as possible. Still, and even with the deficiencies in my knowledge caused by my instinct for self-preservation, I hope never to have occasion to understand or experience the Anattā more directly.