Conservation of Elements

The law of conversation states, among other things, that "nothing is lost but everything changes", when it comes to "producing" elements via the use of Mana.
The existence of magic has created immense breakthrough in the common understanding of physics and the conservation of matter. One great discovery was that the air itself was still made up of elements, imperceptible to the naked eye, but nonetheless finite and quantifiable. While more thorough details about the composition of matter are still hard to grasp, it's fair to say that such a knowledge is already centuries ahead of sciences from the Old World.

Manifestation

Every single form of non-physical magical attacks requires the presence of pre-existing elements to occur properly. Chief examples of this can be found for Water and Earth-based magic. A Water-focused mage can manipulate a set amount of water into different shapes and states, but never increase the actual amount present. Taking moisture in from the air, difficult feat even for experienced mages, but the fact remains that no new elements can be formed, they must come from somewhere. Same for the soil and rocks used by Earth mages.

Fire and Thunder magic, although more complex, were shown to also rely on a form of dependance upon pre-existing conditions in order to work properly.

Type

Metaphysical, Elemental