#Manuela's use of light magic isn't intensive enough for her to really suffer any side effect before the war in either game

[laulink]

The consequences of wielding magic in Fodlan

That’s a headcanon of mine I’m quite fond of (and that I reference in my latest one-shot) : the idea that wielding magic does come with side-effects, but instead of the scars that we sometimes see in fanarts (which are cool, I’m not saying otherwise), those side-effects are hidden, almost invisible, and vary a bit depending on the type of magic you wield. More to the point, it’s not your skin that your magic attacks, it’s your nerves.

The idea is that magic is a form of energy and you generate it yourself, then gather it, usually in your hands, to cast spells ; but just like wielding a sword or an axe often over a long period of time will cause callouses to form on your hands (skin getting damaged by your use of a weapon and being remade thicker so it can’t be damaged again), wielding magic will damage your nerves over time and progressively lead you to lose part or all of your sensitivity over areas of varying sizes.

The thing is, sensitivity isn’t just “feeling touch”, it’s also “being able to identify if something is cold or hot” (or thermoception, which also tells you how cold or hot it is so you can know when it gets too much and avoid getting hurt) as well as being able to “feel how your limbs are positioned” (proprioception).

Those different sides of sensitivity already vary between people (some will be more sensitive to heat than others) and can also be altered by the things that happen to you (a surgery might cause you to lose part of your superficial sensitivity around the area you had the surgery on, like your wrist, which is called hypoesthesia, or on the contrary when the nerves reform they’ll overcompensate and you’ll be hypersensitive, to the point of feeling pain from the lightest touch, which is called hyperesthesia). Of course, in Fodlan, your use of magic can have a similar effect.

Fire and ice magic users (like Marianne) will first be desensitised from heat/cold because the temperature of their magic will get their hands and arms used to higher or lower temperatures and they’ll progressively stop registering them, meaning that the first sign a fire using mage is starting to feel the side-effects is that they won’t notice that a stove-top is too hot to put your hand on and get burned. But their nerves’s deterioration won’t stop just because they don’t feel heat so well anymore and, over the years, they’ll progressively lose the rest of their sensitivity.

Lighting users (like Dorothea) have electricity running down their arms when they conjure up spells and electricity is what is used to send messages by the nerves to the brain, so it will rapidly come to affect all types of sensitivity, but often the first one to be visibly impacted is the ability to feel touch/pressure.

Wind users (like Linhardt) will also lose all types of sensitivity at the same rate, though it tends to affect their proprioception a little earlier than the rest (feeling of weightlessness comes with wind and offsets the nerves).

In a similar, yet opposite manner, black magic users (like Hubert) will also lose proprioception first, then the rest at roughly the same speed, but this time it’s not because of a feeling of weightlessness but a feeling of heavyness from the miasma that is black magic. 

Light magic (like Manuela’s) is a special case because it will cause the caster to lose their vision first (not directly through the magic altering their nerves but because the casters will be exposed to their spells’ particularly strong light) and, after a while, progressively lose the different types of sensitivity at roughly the same rate. It’s the type of magic that is slowest to deteriorate the casters’ nerves.

Lastly, white magic : it cannot actually heal the damage done to the nerves (it’s too complex), but it tries, and the more you use it and slightly damage your nerves with it, the more it will try to heal you as much as the person you’re trying to heal, the more sensitive you’ll become, causing hyperesthesia on an area of varying size.

For all those side effects, there is a cure : not using magic anymore for as long as it takes your nerves to heal (and avoiding any contact, even cloth, on the area impacted if you have hyperesthesia). Depending on how much damage was done, it can take a long time : if the caster doesn’t feel anything up to their elbow, knowing nerves grow back at a similar speed to your hair, you’re looking at a good year of “no magic” to regain your sensitivity.

Stimulation can help with the recovery, which means it can also help slow down the deterioration process while you are still practicing magic : the exercises will vary depending on the type(s) of sensitivity you’re trying to stimulate, but it’s not too complicated to figure out so most mages come up with their own exercices to fit with their lifestyle and available materials and tools.