The Knower is a stage at which the bearer receives a share of authority over the Principles: over those regularities by which existence is structured. The Canon distinguishes here between laws and principles as different concepts, and it is precisely the latter that belong to the Knower.
The meaning of this authority is thoroughly practical for the path of knowledge: by understanding a principle, you gain the ability to use it. Everything the path has done thus far — reading, reasoning, reconstructing events, parsing others' powers — converges here into a single point.
As an Otherworldly of the third stage, he responds to prayers within a certain radius.
The rite of advancement is telling and unsettling: to take apart the flesh and blood, or the otherworldly characteristic, of an angel of the Hermit or Paragon path and to assimilate no less than a third of the knowledge contained in them. Not to defeat the angel — but to dissect him.
The stage's characteristic is described as a tiny tree of clusters of white sharp bones: blood-red brains hang from its branches, and on its trunk open numerous brass eyes.