Pale Blight

Transmitted through ingestion or exposure to thick concentrations of Essence - common vectors are the ingestion of too essence-rich of meat such as that of a Dragon, or through prolonged exposure to beings that transfer Essence through a natural channel, such as a God or Fae .
Theoretically contagious through bodily fluids, but quite a bit of blood would have to be shared to see any signs of poison - IE A Lich and their victim. Otherwise completely self-contained.

When a certain individuals threshold for Essence is crossed, the body's natural's processes cannot filter through the Essence naturally and therefore attempts to expel the excess energy in any way it can. While mostly done through exposure to the Essence of other animals, there are many locations where the Essence in the air can be so dense as to cause initially mild but rapidly mounting amounts of oversaturation and therefore poisoning symptoms.  The cause of the severing of symptoms is simply repeated exposure without or soon after treatment - even after expelling the excess, the body's concentration of Essence will still be far closer to the threshold than the afflicted's pre-incident baseline, causing further cases to spiral further and further along in stage.

CW; Emetophobia. The first paragraph of this a detailed description of vomit.

While the symptoms vary wildly in severity, the most recognizable sign of Blight is the expelling essence-lined vomit that gives the condition it's name. As the most common vector for the condition is ingestion of blood, it is common for the seiged body to send the offending material back the way it came. The result is a visceral ejecta marbled with glowing white streaks of Essence - for the most mild of cases, this is the entirety of the experience. One awful moment and then it has completely passed.   Other Mild Symptoms Include ;

Glowing spittle/tears

Prominent white veins

Nausea

Heartburn/Acid Reflux

Hyperactivity/Restlessness

Nightmares/Insomnia

Spikes in Anxiety/Shifts in Mood

At later stages the above symptoms worsen, in addition to the following -

Sore that tear open on the skin

Bleeding from open orifices

Paranoia

False Memories (And often guilt associated with them)

Delusions of Grandeur

Loss of Impulse Control

Altered Senses

Organ Failure including;

• Blindness
• Deafness
• Liver Failure
• Heart Failure

For mild cases, merely a cocktail of bedrest, lots of water, and fiber-dense foods are needed to make a full recovery - anything mild and plant-based to flush essence out of the system. In some more urgent cases, laxatives will be given to properly expel all the excess. Many magic schools tell tales of miracle next-morning cures or foods made to abate the worst of the symptoms of a spell done a little too indulgently - all with varying degrees of efficacy.   As the condition increases in severity, quarantine is required. Isolation of the patient into a room as devoid of natural magic flow as possible to help the regulation within the body.   In more immediately dangerous cases, bloodletting techniques will be used to regulate essence levels - often done by opening a wound along a vein on the left arm and applying Abata leaves to them to 'pull out' the excess. In lieu of or in addition to the left arm, cuts will also be made along the breast and ribcage .   Once it gets to Stage V, the best treatment that can be given is mercy.

Most of those who have brushes with the Pale Blight do so briefly and get out with only the lightest scrapes. Before The Dragon Crusades , records of the later stages were hard to come by and largely thought of as hoaxes meant to scare younger mages into responisbility.  

Stage 0

More of a scare than an actual stage of infection; its when a mage channels too Essence much into a spell, an unprepared mortal has a chance passing encounter with a god out of disguise, or someone ingests too much Essence than they thought they were prepared for. An unfortunate trip to the bathroom and a learned lesson later, the ailment passes.  

Stage I

Nausea spells begin, alongside a slight glow of saliva and other blood-based bodily fluids. Nightmares plague the victim for a night of restless sleep, before passing in the afterglow of morning. Most common among rookie adventurers and ambitious young magi - colloquially called the "Weaver's Hangover" in some cultures.  

Stage II

Sores full of Essence appear of the skin near major channeling deltas such as around the lymph nodes, under the ears, on the wrists, ankles, and genetalia. The afflicted may begin to hallucinate or recall false memories of a life they never lived, wracked of guilt for deeds they never committed. Takes anywhere from several days to a little over a week to fully recover from, depending on the quality of the quarantine area and how seriously the afflicted takes treatment.  

Stage III

The blood begins to glow from within the veins, the skin begins to lose its color - concentrated around the points of the sores. The afflicted begins to confuse the present for the past, unable to accurately gauge risk or control impulse, and may begin to develop permanent side conditions such as blindness or other loss of sense. It is here when bloodletting and laxatives enter treatment, and recovery is expected to take around a fortnight.    Treatment can become difficult at this stage - as with this stage onward comes a craving for more essence, more power, more of the thrill that only potential energy manifest can give them.   All those who have been to this stage and survived radiate a ghostly glow from their eyes.    

Stage IV

The sores become open wounds from where the skin tears from how taut it's being pulled, and the afflicted's grip on reality slips. Blood and anything else attempts to escape the body as dozens of different realities overlay in the afflicted's perception as if the memories themselves were also trying to find their refuge elsewhere. Oftentimes the best hope at recovering is an extended enforced quarantine with periodic reality checks and bloodletting , and even then it becomes incredibly easy for the condition to worse before it gets better.   Lost to their own desires for what drives them to their death, most successful patients are sedated during the early stages of their quarantine. Magi who let their Blight complicate this severely are often forced into retirement to prevent further bodily harm.   All those who come back from this stage have their eyes permanently devoid of color, left only with milky white irises.  

Stage V

  The psyche's attachment to the material realm and the body's attachement to itself become equally tenuous. Echoes of memories long past comprehension echo in the afflicted's mind, every Tug at the tapestry has a chance of exploding into dangerous wisps of wild magic, and the essence finds anywhere it can go to try and free itself of the cage its trapped in. Fluid fills the lungs, the organs strain at the sheer overwhelm of potential coursing through them, the body may even begin to Augment by itself, and still the mind wants more. Just another sip, and it all sorts itself out.    It is inhumane, then, to let the afflicted suffer any longer.

Stage VI

  Equal and opposite to stage 0, this is less an escalation of prognosis and rather a result. Victims left to fester past Stage V. The body rebels against itself, expunging whatever remains of the living matter contained with it. The blood vessels burst under the pressure, and eventually follows the heart. Left that remains is the purest form of wasted potential - magic rotten past saving in the form of placid, pale viscera.   Those adept in poisons and amateur in ethics find what remains of Stage VI's victims the most potent of ingredients for curse-bottles and other magic-restricting maladies.

Every brush with the Blight increases one's chances of contracting it again , as it is suspected that even after full recoveries, the body holds naturally holds onto a little more essence in the blood each time without raising the natural threshold. Thus, those traversing Essence-rich terrain or doing involved spells much take care in training their own body's resistance and continuity in the flow of magic, or fear just getting sicker and sicker until they're forced to retire or worse.   A most common lasting side effect from more late-stage iterations of the Blight is blindness, especially from Stages III and IV. Most easily recognized by irises completely devoid of color, the afflicted's vision is worn down to the point of only seeing auras and threads of magic. This is sometimes called the "Eyes of the Seer".

Before the days of the Dragon Crusades, Pale Blight was a word of warning to apprentices of sorcery and other weaving arts to stay within the limits of the gifts the Gods gave them, or train methodically to gradually surpass one's limits. It was the direct result of a terrible choice - a lesson learned through the digestive tract and a story to tell come morning. Records of anything past Stage II were often mythologized in the stories of mad wizards and those who dared to make themselves gods, not thinking that any sane Memdian would try.   Then, came Augmentation.   On the ground floor of the science of changing one's body beyond the weft's limits came grevious consequences - soon the symptoms of cynical sorcery came to life on tavern floors, in the depths of dungeons, and on underground operating tables. Many saw it as a sign of the true end times, others saw it as a sign of a people brought to the brink beyond desperation, others saw it as a push to go further. The Stages were codified in the blood of Crusaders and information sent out as a warning, but it wasn't until the formal sealing of the Laubidaigh Passage and the end of the Crusades did people stop dropping like flies with a vial of dragon's blood in their hand.   Ever since then, though, even stages III and IV have become more common among wayward wizards across the globe, the reason behind which there are many theories. Whether it be some kind of divine punishment or just the concentration of Essence on the planet increasing one way or another, as of 1107 AUE is has become clear that after being thrust into the spotlight, the Blight will never fall into obscurity again.