Arcane Potential

Arcane potential is defined as the core ability of a magic user. It is an inherent quality over which one has limited control. All individuals are born with at least a small bit of magic potential but for most this low level of ability would cause them to struggle with the most basic of magic. While those born with higher arcane potential are able to wield much more powerful magic, this higher potential comes with a number of severe drawbacks. These drawbacks can affect the user's general health, mental control, and in extreme cases their personality. Arcane potential can be increased, but even attempting to do so is an extremely dangerous and often fatal challenge. (Despite the use of the word arcane, arcane potential affects all types of magic, not just arcane magic.)
Description by Kherson Moria, The Sage:
"Arcane potential is like fire. Most mortals possess only a spark, a single pinprick of light and heat. And similar to how a spark provides little in the way of light or heat so too does that individual's magic potential pale next to others. There are some individuals whose potential is like a candle, others still whose potential is like that of a stoked brazier, and those whose potential blazes like a great hearth. There are some though, whose potential burns greatest, like a forest fire, and it is from these individuals that the greatest and most terrible practitioners are found."
(For game rules see Arcane Potential)