Kotro (Kot-roh)

Summary

What happens when a mage, rather than drawing upon their own internal mana, uses the environment's instead? What exactly is the limit, and what happens when it's hit?
The phenomenom around such an event is, in the jiuweihu vernacular, kotro–"getting slapped back". How it manifests depends on a number of circumstances, but its an important part of magic and its consequences. To start, there are two 'types' of mana within everything: intrinsic, and available.
Intrinsic mana is apart of the thing's structure itself, what gives it form, shape, and function. Drawing out this mana is not only much more difficult, but directly damaging to the thing it is part of. Something like a rock would crumble into dust if its intrinsic veltron was completely drawn out, for example.
Available mana is akin to abundance, excess used to grow more of itself, the thing its apart of, and so on. This mana is the easiest to take, and what many mages will work with when doing external sources of power. Using the veltron example again, there is a lot of veltron mana available wherever there is dirt, stone, and so on. The veltron mage struggles more because of the different sediment types than mana availability. Wind mages, by comparison, also have an extreme abundance of mana but it is much more dispersed, and so must be 'gathered'.
Once the available mana has been used up, the thing will try to return to its natural state of being. When a mage tries to extract everything, including the intrinsic mana, then kotro begins growing. Like an elastic cord being pulled, the more intrinsic mana consumed, the stronger the inevitable backlash becomes. It also becomes increasingly difficult to extract intrinsic mana, as if the sources themselves begin resisting more and more. It takes a truly powerful mage, or other magical person, to not only extract it, but resist the incoming kotro as well.
Every culture across Veltrona has some awareness of, and history with, kotro and its effects. In a broad sense, most boil down toward lessons warning against greed, over reach, and/or upsetting the natural balance of the world. It is among the first lessons taught to any mage, cultivator, sokral, and anyone concerned about using mana-hungry forms of magic.
Consequentially, kotro can be called the reason why many magical arts emphasize growing one's internal power rather than using external sources. Of course, enchanted gear, items, and other things rose to the challenge nonetheless. The creation of material things that have abundant amounts of available mana is where a lot of smiths, engineers, and the like built their craft. In essence, mana batteries, though actual magic can also be enchanted upon the gear.
It's worthwhile reiterating that kotro as a phenomen only occurs during extraction of intrinsic mana. As many magical arts have been built upon foundations of understanding this process, they do not typically cross the line. Anyone following modern magical arts shouldn't encounter kotro, and even in situations like war it doesn't arise regularly. Those who are foolish, ignorant, or desperate, however, may push beyond their limits for more power and so may trigger kotro.

Causes

Extracting and overusing the intrinsic mana of available sources will trigger kotro's growth and subsequent backlash. This includes the magic person's body itself, which will desperately resist being consumed in order to survive.

Symptoms

The mana sources being extracted upon rapidly decay in varying ways. As an example, Veltron turns to dust, wind becomes stagnant, water evaporates, fire burns out although that is a hard to distinction to see per say. Physical objects comprised of that mana exhibit more complex degradation effects. Since many things are not always composed of a singular type of mana, the removal of one particular type causes an imbalance. The resultant imbalance is normally quite catastrophic, but how that is expressed is a truly varied problem.
As to the thing that is extracting intrinsic mana, the backlash itself manifests in a number of ways. The body, device, organ, or other specific part is normally struck by a mana surge similar to an actual magical attack. A person's body may also suffer an intense bout of manaesia, especially if the extracted mana isn't properly controlled. Failing to endure the backlash can engender devastating consequences, especially if a lot of mana extraction is on going.
Those who are too greedy are quite liable to explode in a gruesome end. Those who endure before then may develop all sorts of complications or conditions, and permanent injuries is a possibility as well. Generally, the more backlash is allowed to run rampant, the worse the consequences will be. Some mages have only survived by sacrificing parts of their body to divert the damage.

Treatment

As the kotro backlash is analogous to a magical attack, treatment depends entirely on how it manifested. Rest and care can handle almost all accidental or small efforts, provided the victim isn't unlucky with how it happens. Stronger kotro may inflict deep tissue damages, which are among the worse problems to treat without healing magic.
For people in particular, nerve damage is also a serious concern as the kotro can manifest erratically if not controlled. There are some recorded instances of organs, vital nerves, bones, and other parts calcifying, burning to blackend lumps, liquifying, or expanding violently.

Prognosis

Luck is a truly meaningful component toward how viable treatment can be. Since kotro itself is essentially a magical attack, the outcome of it depends on what happened exactly. Permanent maiming and death are common fates, especially among inexperienced and naive mages.

Prevention

Skillful persons can potentially direct the backlash to protected or hardened areas, be it their own bodies or otherwise. The issue is the cost in doing so almost always exceeds whatever value they gained from the mana itself. It's a nasty surprise and one of the fundamental reasons why intrinsic mana extraction is considered unviable.
Those without the skill, or facing too great of a kotro surge, may instead have special equipment they use as a sort of 'in between' solution. By sacrificing the equipment, they protect themselves without having to spend mana in doing so. Of course, one must weigh the cost of such equipment in the equation then.
Manavores, in particular, are intimately aware of intrinsic mana and have evolved their own solutions toward handling it. Many do not ultimately go for 'complete devouring' of mana. Once the available supply is gone, how each species dips into eating intrinsic mana varies. Generally, they go as deep as they can to safely endure kotro, then discard the husk left behind. Their physiologies are better adapted at taking on the kotro backlash, and some even use it as part of vital processes.

Type

Magical