Mana
From Legonia
Mana is the basement of all kind of magic.
Scientists and theologists see mana as the 5th element in the holy category (Fire, earth, wind, water, mana).
Mana can be found in everything connected to one of the other 4 elements, so also in every lifeform. Those races, which are born with a natural skill of using magic have big concentrations of mana surrounding them. Using spell magic means to manipulate/interact with the mana of your environment. That's the reason why natural mages are more powerful than other ones.