The Elemental Alphabet is said to be so old that it pre-dates any other written language. Whether true or not, the characters are very old. There are 27 letters, each based on elements or combinations thereof, and they have a secondary meaning beyond the sound they represent. In writing, this secondary meaning is not used very often, but it is crucial in magical writings and incantations made with the alphabet.
Notably, each language that uses the Elemental Alphabet avoids using letters from the opposing element, in fact often lacking the associated sound in the language itself. This means to one who speaks Aquasian, certain letters will appear to be in Ignus writing that aren't proper letters to them, while other crucial letters are missing entirely, making Ignus writings seem like gibberish to Aquasian speakers, for example.