For some creatures, magic flows naturally through his or her veins, while for others, it is something that is sort of discovered. Through exploration and training, it can become a useful tool and the user's most powerful weapon. We call this magic "elements." There are many different types of elements, some weaker than others, some stronger, and some darker than others. Certain creatures have only one element, although this is rare. But most have two, and are not able to have anymore, as their bodies wouldn't be able to handle so much power.
Only Leafs of high rank (leader, co, advisor, etc.), are able to have three elements.