When the walls between worlds are breached and something entirely other crosses over, the violence of the invasive contact causes immediate, gruesome and fatal mutations.
Over the course of my travels it has become clear that the physical laws that govern our world are not as immutable as we might once have thought. They can be bent, subverted or circumvented - making the impossible possible - and, in the most extreme cases, can be so brutally distorted that they break entirely. Even, perhaps, irreparably. In particular, the intrusions of extra-dimensional objects and beings into our three-dimensional reality have proven to be some of the most physically, psychologically and philosophically traumatic phenomena that I have ever encountered. The incidences of such destructive contacts vary wildly, but the most common of these admittedly uncommon events, accounting for some 60% of incidents, share enough characteristics to have been catalogued under a single name: Greywalk Occlusions.
The total absence of observable precursory signs immediately sets these apart from other cross-dimensional visitations. Where those are variously announced by the breaking down of physical matter, pockets of ruptured time or similarly measurable overtures, the Greywalk Occlusions begin with the abrupt manifestation of the figures of those who have journeyed to our plane. Although broadly human in their configuration, their bodies appear to be comprised of shifting angular facets in a palette of gloss greys, a sight which, like optical illusions, the eye struggles to bring into focus and the brain struggles to interpret. It is unclear whether the shifting physical structure of the travellers is a reflection of their true visages, some technological contrivance which allow them to cross over or, maybe, their multi-dimensional nature forced ill-fittingly into our standard measures of depth, breadth and height. Nonetheless it is apparent that they are, uniformly, several times larger than even the most massive of human beings.
Having arrived, the disruption of their presence begins to affect the world around them in jagged, imperfect spheres of influence: Inorganic and organic matter alike - though per my research and to the best of my knowledge these phenomena have only occurred around plant and insect life - begins to mutate, maintaining its aspect but becoming transformed into monochrome facsimiles of living, pulsing flesh. The colour around them drains away, lights either no longer reflecting those wavelengths or manipulated, somehow manipulated to give everything around them a hue as bleak as the moribund flesh being created, whilst a rasping mechanical drone fills the air at such a volume as to drone out anything less piercing than a full-throated scream. Surrounded by the damage they wreak, the beings take a ponderously slow step or two, as if the makeup of our reality is some thick, turbulent miasma to them, before disappearing in a flicker of being there and then gone - vanishing as abruptly as they first arrived.
Greywalk Occlusions have been sighted across the known world except, obviously, in the Olmec Null, with the ground they cross and any life they corrupt typically decaying to brittle ash within a few hours of their passing. Since this process leaves the sites apparently appearing to be little more exotic than the aftermaths of intense localised fires, they are a particularly difficult phenomenon to track and research effectively. In fact, between any ambiguous incidents and those sites which have been staged with the intention of drawing and exploiting those who, like me, have an interest in the esoteric, there are innumerable false leads. Nonetheless I have travelled to the locations of eleven occlusions, reaching one site only two days after the Occlusion was witnessed, and have discovered or confirmed several of the lingering aftereffects: the stress fractures in the fabric of our dimension.
The most immediate impression was of a slight deadening of sound coming from outside the sites, the aural landscape permanently weakened, perhaps by some unknown quality of the aforementioned mechanical droning that accompanies a Greywalk Occlusion. Those inside the site are able to communicate normally, but anyone who passes the unmarked boundaries has to raise their voice to be heard at all and still sounds muffled. Perhaps relatedly, any exposure to the sites lasting longer than a few minutes triggers migraines, even in those not previously prone to them, with accompanying visual artefacts of gleaming halos that encompass the sufferers’ whole body. There are no lasting ill-effects from this temporary exposure, as far as I can tell, however the experience is debilitating enough to force most away from the sites and keeps many from returning. Foremost, however, I was able to ascertain the echoes of the event as they pertained to the mutagenic.
Although the flora, fauna and terrain which were transformed into flesh in the initial incidents die and turn to ash shortly thereafter, it seems that the sudden shock of such rapid mutation is an important factor in the brevity of their lifespan. Whilst the ground can recover, the ash actually seeming to promote new growth, any plants that grow there are shot through with veins of the same greyed flesh that was evident during the initial incident. Unable to be cross-bred, or even cross-fertilised with healthy examples of the same species, they grow and die fruitlessly, needless horrors eventually rotting back into the soil to begin the cycle anew. At some of the locations the ground has been salted to slow or stop new growth and spare the queasy sight of these perverted, unearthly growths.
Whilst wildlife that passes through the echoes of Greywalk Occlusions seems unaffected, particularly when set against the reaction that human explorers experience, anything that eats from the infected flora is poisoned. Having eaten or drunk from these plants, animals quickly fall prey to convulsions so fierce as to tear chitin from its fixtures or snap the bones beneath straining muscles. Even watching this happen to insects is repulsive, but I saw a rabbit undergo the same torment and I retched uncontrollably. Later I watched the rabbit being dissected, its broken body full of blood-heavy tumours which must have grown and metastasised at a desperate and agonising rate. I have not seen whether the same applies to humans, but the logic of salting the sites to retard new growth seems an eminently necessary precaution.