The image already on the page should be just fine. It is the universal symbol for magic in the Salenzian world. Each triangle is one of the elemental schools.

As for the paragraph:

Magic on Maikros is powered by mana, a sort of field that mages draw from to do things like create fire, heal others, move hills, bend space, etc. There are three kinds of casters: studied, intuitive, and innate, in descending order of knowing what they're doing. There are also two ways to cast magic: spark magic, which is quick and dirty, and formulaic magic, which is complex and requires a lot of preparation. Otherwise, Maikrosian magic is divided into schools. There are seven elemental schools, shared across almost all cultures. Though, what exactly each school covers can vary from culture to culture. These schools are fire, water, earth, air, nature, light, and darkness. The only cultures that do not share these schools are those of the ansu, which instead have schools based on their gods. On top of these basic schools are the nonelemental schools, which are in some way derived from the elemental schools. This is an open class, subject to revision whenever a new school is invented. The nonelemental schools are known for being difficult to master, because they require using unfamiliar or overspecific concepts, unlike the basic, broad, well-known concepts used to cast elemental magic. Then there are the mana spirits - one kind for each element - who govern the Mana Cycle, with the intent of preventing its depletion, and so punishing mages who cast too-large magic. And the Underworld, which holds infinite mana, but has its own great dangers.