Guild Glyphs

Guilds are built on secrets as much as members, and the need to record and protect those secrets is paramount to their leaders. While many guilds keep their records in complex codes and ciphers developed by their cleverest and most devious members, these cumbersome secret languages are of little use to the rank and file. And yet the men and women on the street often have a need to communicate covertly with one another.
So was born the informal collection of languages known as the guild glyphs.This system of symbols allows guild members to leave messages for one another on the streets without worry that their rivals will intercept them. Each guild develops glyphs that are most relevant to their chosen territory and area of expertise. The benevolent Protectorate, for example, has glyphs that identify at-risk targets, safehouses, allied businesses, and hidden caches of weapons or armor its members might need. Meanwhile, the nefarious Breath Takers mark the location of broken locks that allow easy entry into apartment buildings, locations where the guards rarely go, and the routes taken by potential victims to and from their homes.
While this system works quite well, especially for guilds with well-protected territories, there is a constant race to upgrade friendly glyphs while subverting the glyphs of enemies. In areas where territories overlap, rival guilds will try to decipher hostile glyphs and repurpose them to deceive and endanger their enemies. This practice often lead to elaborate "stacks" of glyphs that are so confusing and treacherous they lose all value as anything other than historical records of conflict between two guilds.
Of late many guilds are complaining of new and mysterious glyphs in their territories. While they do not seem to be overtly threatening, the presence of these new glyphs worries guild leaders that there might be a rival coming up under their very noses.