The Fate & Corruption of Magic

Magic by it's nature is highly mutable & volatile. This bleeds out when in the Material Plane that can be warped by the effects of it, especially in concentrated regions and through heavy manipulation of it.

Transmission & Vectors

Most cases of transmission is caused by the act of channelling magic through the use of spells & rituals, tapping the raw energy of magic.

Causes

Magic is inherently neutral in nature and a form of energy that flows through & binds many Planes together. It is mutable and with the correct mental fortitude can be tapped. When this happens it flows through the user like water through a sluice gate being shaped by thought, action and / or components. When this happens, it leaves a residue behind, a little bit of it's make-up in the body & soul of the user. Given time the user will find that the mutability of it starts to work on them, sometimes for the better, sometimes for the worse.

Symptoms

When this mutability takes effect, it can alter the creature's mind, sometimes for the better, other times for the worse. In many cases it seems to be affected by the spells used, with the mind of a necromancer or battle mage for example, giving them thoughts of death or bursts of rage. Elements of the magical energy then starts to mimic these thoughts, making it easier to draw on strands of magic that closely resembles (due to mutating into similar patterns) those spells creature prefers to use.
After a while, the creature starts to mutate physically. Slowly at first, then as age takes it's toll, the creature will show greater physical effects. This seemingly appears greater in Warlocks, than Sorcerers and Wizards, partly as to the domains of their patrons affecting the magical source of their powers. Sorcerers can still be affected due to their family bloodline or other source of their power. Wizards are rarely affected due to how they learn their magic.
In the physical side, strange coloured patterns or types of hair or eyes, or skin colouration or patterns can appear. Sometimes strange extra digits appear on their hands / feet, or some end up missing or fusing together. Webbing between them, or between the body & limbs can grow over time. Organs, teeth, skin texture, bone grown and head size / shape can happen. Extra organs such as gills can develop, or the bones hollow out like a bird's. Strange biological or biomechanical structures can appear to grow out or replace body parts in some, yet predominately seen as such in ancient bodies found in tombs, or under certain conditions (like fallen bodies in the permafrost or peat bogs).

Treatment

The safest treatment is to stop using magic, and eventually let it dissipate over a length of time from the body. Any mental health problems caused may be treated with regularly consulting a Wise Man / Woman, the shaman, a Hedge Wizard or a Priest to name but a few. In the case of physical changes a physician or Barber Surgeon may be called upon to carry out a mix of surgery and / or alchemical treatment to deal with these side effects. In rare cases, an exorcism of some type may be needed if a patron is involved, or similar source of magic.

Prognosis

This depends entirely on the state of the patient / mage. In the early stages it can be treated easily and safely. At the later stages nothing short of an exorcism, Wish spell or divine intervention can hope to cure the victim. Over time it will get worse and become more pronounced with greater chances of physical deformity appearing as well as possible dangerous phycological conditions or outlooks.

Sequela

There is the risk that if the magic following through is unchecked then the creature will become less & less like the species they were. If this happens then they run the risk of their body & mind / soul becoming completely alien in every sense of the word. Separation from their parent species can happen and even at the earlier stages certain members of their own species feels as if there is something not quite right about the individual.

Affected Groups

Magic users, especially Warlocks and some Sorcerers  (and the odd Wizard), are the main groups affected. If a region is seeped in magic, then any creature could be affected to a greater or lesser degree.

Prevention

The only safe way is to avoid the use of magic in the first place. If not, then certain guidelines are used in many societies. This will prevent certain types of magical use being taboo or outlawed. Others will put specific training in place to avoid unwarranted corruption setting in, or incorrect handling / casting of spells & rituals especially by those not formally trained to do so.

Epidemiology

Underground cults and magic schools are the main source of these, and little formal study (usually by a lone individual) can cause this to manifest. In some rare cases, the build up of magic in a specific space or individual can bleed out so to speak affecting others, or even the environment, in some instances. These can also attract strange otherworldly creatures to them that makes the magical energy more dangerous and powerful.

History

Millions of years ago when the Dragons arrived on Earth when it was young, the Great Old Ones arrived too. Both are highly magical and brought this knowledge with them. At first very little was affected but after a while other life evolved and the magic produced by both started to affect it.
The Dragons had the benefit of being born of the Material Plane, and their magic is tied solely to this plane. The Great Old Ones weren't. This started to affect the life in unforeseen ways, and with their already mutable bodies & the Far Realms being their original home Plane, regions of the world and the life found there started to mutate. Most carried on naturally taking in an element that lent them a certain ability to manipulate portions of magic in safer ways. Others though, were not so lucky. One was early hominids. When the Hyperborean Age appeared, humans and many of their closest relatives had moved out, and few practised magic. Their were a wild form and they had many deities teach them different magical arts. Most were fine, while a few took it to extremes appearing as beautiful heavenly creatures to some, or grotesque demonic monstrosities to others. Eventually war and the breaking up of Pangea drove the majority to extinction.
Whether by chance or the meddling of some higher power, modern man and other hominids arose over time again, and they had less of a connection to the powerful magical forces that were present in earlier times. The distance of time & space of the continents helped to separate them from the past, the Dragons & Great Old Ones vanished into myth with most dying out and those remaining retreating to their lairs to sleep away the centuries or aeons until some future date. Now most that remain are stirring again, and that ancient, powerful and highly dangerous magic is starting to build again slowly. Despite the drop in numbers and most of it cut off from the world there is always the risk the wrong creature may become privy to such a source again.

Cultural Reception

Most are avoided, due to fear. The possibility of it affecting others may be slight but most are well aware that magic that's not controlled properly know that 'accidents' do happen, and the victims are viewed as too dangerous, in league with powerful unfathomable entities, or as devils.

"I've seen the effects of unbound magic on the human body. One man, who claimed to be a Warlock with a patron living under the sea west of Brittany, had become affected. His body had an amorphous fish-like quality to him. Big bulging black eyes staring out of a fishy face, skin slicked with oil, slight scales of greenish yellow on his skin too. His hands & feet were webbed, and his teeth were dagger shaped. He'd talk in a gurgling voice, and liquid would pour out of slits on his neck.
One day he got up and said he had to go to a cave in a large hill near the coastal fishing village he lived in. Said there was a similar man such as him living deep within it. Described him as a Warlock too, with thick hair-like structures growing out of his head, and a skull-like face with sharp teeth. Wore metal & leather-like armour of some type, and worshipped a god under the ground and long forgotten by most.
After a few hours we were woke from our sleep. The ground was shaking and the sound of what appeared like thunder could be heard. This must have lasted for a good half hour. Terrified us.
We waited to the morning and got a group of fighters to go down into the cave system. They found nothing down there except strange growths on down in as if they were made of a mix of living tissue and metallic imitations resembling many strange mockeries of objects and growths. A good many of these were damaged beyond recognition and no bodies were found. It looked like a battle of magic had took place there, but no bodies.
Either way, the local druids came to us and said that they had felt a shift in the magical energies that flow through the lands here and it seemed more at ease since that time. After that, we all slept better too."
Militia Captain Marcus de Breton, stationed near the north west coast of Brittany.

Type

Magical

Origin

Magical

Cycle

Chronic, Acquired & Congenital

Rarity

Rare