The Ishvara pathogen is named after the Hindu concept of Ishvara, chiefly for the juxtaposition of being the same and yet different from creation at the same time. It's to be understood as a partially sarcastic name, given that no matter how overwhelming it may be, it's neither a deity nor anything strictly pleasant.

Ishvara in its raw form resembles a black liquid, surface pitted rather than smooth, vaguely crystalline in appearance, albeit not in structure. Aside from a tendency to stick together given slight magnetic properties, Ishvara is probably best likened to sand in actuality. It's inert over any amount of time, possessing no life of its own, needing the steady warmth and biological infrastructure of a host to function. It was artificially created by Deiparous Technologies, meant to be a base-line neural augmentation with little to no function of its own, but capable of enabling a whole array of sophisticated sub-augmentations.

It's probably this expected passivity that let Ishvara get terribly out of hand.

Theoretically, a single grain of Ishvara is enough to infect a human being, but the substance isn't robust except in groups (part of the reason it has magnetic properties, clustering together for protection). An injection will always result in infection. Ingesting a visible amount of Ishvara has an overwhelming likelihood of infecting the host.

As Ishvara nests chiefly in the neural pathways of the host, by default the breath or saliva of an infected host will not contain Ishvara. The blood of an Ishvara victim will contain amounts of the substance, however, and should be avoided.

The symptoms of a person infected with Ishvara tend to progress quite rapidly, as the substance is perfectly tuned to handle human physiology. Within one minute, a mild sense of burning will develop in the host's body, most prominent around nerve clusters like the solar plexus. Within another minute, depending on the sensitivity of the host, a cranial pressure will be tangible.

The rest of the symptoms will vary greatly as the further advance of Ishvara tends to be personalised and ranges from a sense of ones thoughts being cleanly separated and interleaves into or a gradual fading of consciousness to an alien loss of motor control and increasing uncertainty about the authorship of one's thoughts.

From the outside, the personality of someone infected with Ishvara will never completely vanish and they will never appear 'soulless' unless deliberately manoeuvred that way. What remains of the person on the inside varies greatly, depending on how malleable and useful their personality turned out to be, and how great the host's attempt to break out of the Ishvara creature's control were. Either way, one can easily hold a conversation with a single Ishvara case without getting the impression of neural or intellectual deterioration.

In actuality, Ishvara manifests by rewriting the host's brain. Most of this rewriting is not destructive - it's rearranging information transparently - but ultimately, it creates a niche for itself and effectively establishes itself as a further brain module. It can take a long time (relative to the abrupt shock of infection) for the transformation to be complete, though most of it is entirely invisible and intangible, even to the host, except in effect: The astounding benefits of the pathogen only set in after about forty-eight to fifty-four hours (see 'Abilities').

In many ways, the effect of the pathogen is like assimilation - the adoption of the individual into a greater whole, that thinks as one. In other ways, it's not remotely comparable; the individual does not hear the thoughts of the other infected and in many cases, even retains some of its original autonomy, beyond just the one a single module of the creature would enjoy.

Nonetheless, a creature does exist.

The Ishvara creature is the result of infected humans networking together telepathically. This distributed consciousness only exerts as much control over individual infected hosts as necessary and does so abstractly, rendering classic 'collective mind' effects such as speaking in unison or collective, identical motion absent.

Similarly, an Ishvara case isolated from the others might no longer be able to follow the commands of the creature, but is likely to be formidable on its own, with the creature's agenda having long since infiltrated its nervous system like a memory that cannot be erased.

Those infected with Ishvara develop a few very prominent psychic abilities, most notably pyrokinesis (for which Ashfall is named), telekinesis and telepathy. Telepathy is a magnitude stronger between those infected by Ishvara (even the freshly infected) than it is between an infected and a person without Ishvara.

Generally speaking, the strength of these powers depend on the distance it must cover. For example, it's easy to immediately render a human close enough to shake hands with to ashes (if the Ishvara infected were so inclined), but it might be difficult for their telekinesis to find purchase on a plane flying overhead.

The powers take around two days to fully manifest. In most cases, they'll be entirely absent before they flower into existence, but some people may - very rarely - show weak hints of them starting as early as five minutes into infection.

Ishvara has a limited ability to streamline other aspects of the host body, chiefly by cleaning up metabolic inefficiencies, but these tend to take even longer to manifest - certainly nothing under a week.

Generally speaking, those affected by Ishvara can still be killed in any way a human being can - assuming their telekinesis doesn't save them from it, e.g. by stopping bullets or displacing a cloud of gas. They also still need to eat and drink, although not quite as much as a human, their metabolic system streamlined. Nonetheless, especially when more creature than individual, they may potentially forget they need to sustain themselves as a single unit and burn energy they don't have. In a way, the pathogen in its ability to subsume so many individuals does not necessarily correctly assess the needs of this small part of itself - though it'll be an absent-minded oversight, not lack of care.

Those affected by Ishvara do not commonly feel fear - their death would be fairly inconsequential, given that their 'collective' remains largely untouched by the loss. Beyond that, they adopt many or most of the traits of the pathogen's collective personality, but internalise them as their own.