The group known as the Knifemen, The Knifeman's Guild, or simply The Guild, consists of individuals linked together by the general will of the Guild.
The Knifeman's Guild acts as a repository for information. It goes about gathering this information by offering the unique skills of its members in exchange for information or for something that may bring them closer to some ancient piece of lore. More insidiously, the Guild will also lend out its members so that they might be placed in a position from where they can gather knowledge.
The Knifemen most commonly acted as postmen, assassins, and scribes. Due to their incredible skills, they were rarely turned down.
It is hinted at in certain texts that the Knifemen have another more specific purpose, but ironically, this information was lost in the vast collection of knowledge in the Guild.