Magical Barriers: Function vs Mechanic

A magical barrier is something a practitioner of magic cannot do without if their skill set being learned has any combative application. Therefore it is wise for them to learn at least how to spin a basic personal barrier (this would of coarse make it easier for the practitioner to learn telekinesis as well, but that's another lesson...).

In essence, a barrier spell is composed of elemental weaves in a warding matrix which would encompass a static location by being anchored to an object or person. It works like so:

(Elemental weaves + Anchor size) x desired barrier Strength = POWER required.

As you can see a small barrier requires limited energy and concentration to maintain, however, a larger barrier would draw exponentially (to the 4th power) more energy and concentration to maintain. Hence the high fatality rate of mundanes around magical combat. There's only so much attention a magic user can maintain. There is a way around this though- a gifted magic user can use only certain elements in their barrier spell instead of the whole bag of tricks thereby substantially decreasing the amount of energy and concentration required. It can be a tad risque, but in certain situations it can give a much needed edge on the competition.

For example. Instead of weaving the full bag of air, fire, earth, water and spirit into the barrier, just weave air and earth with a to stop physical strikes. Or weave only fire to stop any physical contact from anything living.