Ars

The basis of all magic, Ars is the word used to describe the primal force that motivates magical activity as well as the actual physical, mental, and verbal components needed to perform it. 
In its most primal form, Ars is a dangerous to control force, the knowledge of which was passed down partially by the Faen to the earliest First Oneran Emperor, Oneranus the First. Even the most rudimentary understanding of this force gave the early sorceror emperor great power over the material and immaterial worlds. This power seems to have dwindled over the eons since the egress of the Faen from the world, as well as grown more dangerous to manipulate. While it is said the earliest practitioners of Ars could draw all the precious gems out of a mountain with an act of sheer will, modern practitioners have far more stringent limitations and run far more dangerous risks for such acts.
Few can claim mastery of the old ways of magic today, and those that do jealously keep its secrets and protect its mysteries.

Source

Scholars have debated the origin of this power, but a common metaphor used is that it is powered by the "untapped immaterial." Famed scholar Andantino the Poeticule once remarked that the source of Ars power seemed to be "the selfsame source that gives unshared secrets their power" and "the power of selfless love," and "that quickening that comes in the penultimate of breaths." Whether that is factually true or a simply overwrought poetry is a matter of much debate.