In the beginning, the Creator spoke four words of great power: the celestial words for Earth, Water, Fire, and Air. From these words and the Creator’s power, four great skeins of power were created. The Creator strung His loom with these energies, and wove a world. That world He named Leshtava, and the power of his Words coursed through the very fabric of the plane.
All life on Leshtava is effected by the elemental forces of the world to some extent. Trees made of ironwood grow over some strong earth lines. Sylphs gather to feed on energy from the air lines. Dragons breath fire by awakening the energy in a fire line. Nymphs raise or calm storms by adjusting lines of water. These are natural phenomenon, just as natural as an otter using a stone to crack shellfish.
Most species are tied to one, maybe two elements. In that respect, humanoids are unique: although individuals are tied only to one or two elements, the race as a whole draws from all of the elements. And just as humanoids can differ in elemental affiliation, they can also differ in elemental strength—just as they can differ in physical or mental strength.
In Leshtava, you take on the role of a hero who not only has his or her own physical and mental attributes, but has ties to one or more of the elements. The strength of this tie is determined in the same way that physical and mental attributes are determined; it is considered to be a different ability score.