The Gloranthan runes are basic building blocks of Gloranthan magic. Gloranthans have always used various symbols to express the great forces that underlie existence. Although the meanings were kept secret, the forms were usually quite visible even to enemies. Over time people began to recognize each other’s signs and to correctly identify many of their traits and powers. In that way people used each other’s runes for similar powers. Thus, the Orlanth sign became widespread as the Air Rune even among their foes. Both uses are correct interpretations of the power of this rune. Of course, many times people attached false impressions and prejudices to their enemy’s runes, and in local traditions these presumptions still exist. Such prejudices contribute greatly to the tensions of the Hero Wars today, as they did in previous Ages.
Here is a document describing the Gloranthan Runes.