Mental

Introduction
The Mental (or Magical) branch of the Magic System is by far the most complex. It comprises all things thought and memory based and subtle effects all living things even when not in active use.

Mana Pools
Every living being has it's own mana pool consisting of mana power, or MP for short. This mana pool charges over time (faster while sleeping) and is drained by taking any mental-based action. This includes moving your body (picking up a pencil, or walking) and casting spells. Granted, doing minimal tasks like lifting your arm or chewing require so little thought/MP that it is negligible. But the same energy that is used by your brain to tell your arm to move or to think up the answer to a jeopardy question is also the energy used to cast magic.

although MP is not technically the actual physical bio-electric energy in your brain and nervous system it is used in the same way and for the same purposes. Using MP will mentally exhaust you in the same way that doing mentally strenuous or stressful things will, such as staying awake too long, dealing with too much stress, or thinking too long/hard about various subjects. The more you use magic the more sluggish your thoughts and mental faculties will become. Using too much MP will cause you to reach the critical point where your body will shut down access to your MP in order to prevent death, Running out of MP causes living beings to become brain dead. The critical point can be passed however if someone trains to do so, but it is not advised as not only would using that MP kill you, doing so consciously would count as suicide.

A lethal tactic among some mages is to drain the entire MP reserves of their target, rendering them brain dead or dead. This ability is incredibly difficult though and requires a very specific type of mana draining ability, as a person's brain will resist access to that 'reserve' MP as viciously against an attacker as it would its owner. Since this reserve MP is the last bits of MP used to power and maintain a user's brain, when an enemy absorbs it and kills that person, it is not uncommon for them to acquire fragments of their victim's memories and possibility even learn something of their abilities.

Spell-casting
The process of casting a spell technically begins with the manifestation of a bit of magical energy in the form of raw mana, known as Arcane Energy. Most schools, however, essentially skip over this step as most of their spells inherently manifest the arcane energy unconsciously and immediately convert it into their spell the instant its generated.

Manipulating arcane energy itself is significantly more difficult than simply casting a normal spell. Arcane energy is unnatural and is not meant to exist on its own in its pure arcane form. It 'wants', for lack of better term, to be some kind of spell, or to simply dissipate back into non existence. Any stray uncontrolled thought while handling arcane magic can cause it to spontaneously form into a spell or simply destabilize and explode, which is why most mages never bother learning to manipulate magic at an Arcane level.

Arcane magic itself is most often only used for magic that specifically effects other magic. Spells meant to do things like dispel other magics, or create barriers designed to specifically reflect magic are all done through arcane energy. Its the difference between creating an arcane energy barrier to stop the magical energy that a magical fireball is comprised of, and creating a barrier out of kinetic force to stop the physical impact of the fire itself.

There are many different ways to cast spells, some easier than others. Most spells are cast through some kind of channel or medium that is used both to guide the caster's thoughts and intents. Whether it be reciting an incantation, making elaborate hand gestures, drawing runes or glyphs to complete Magic Physics equations, or any other number of ways all of these are simply 'paths' to channel mana in which to create a reaction.

The Expanse
All thought's that ever have, are, or will be created have existed and always will exist as part of The Expanse (The Collective Consciousness). The Expanse is a 4th dimensional concept, which means that it exists simultaneously at every point both in time and space all at once, permeating all of existence. When a person thinks, they are actually channeling thoughts from The Expanse.

The Expanse is known to have an effect on the fundamental laws and mechanics of all magic but the specifics of these effects are not well understood. There are only a few things like Society Magic which it is known that The Expanse has a direct influence on specifically.