"Those markings... You are more than just a random mercenary, aren't you?" Wingard Brighthand to Mhurren Freeblade.
Glyphs are special markings that carry magical properties. They are carried by individuals who can wield their power. They are considered to be of the same nature as enchantments, conferring particular qualities upon whom they are bestowed. A Glyph can only be applied through branding, so those who seek them must be willing to make that sacrifice. In addition, very few people actually know how to create Glyphs, making them a rarity.