The ravenkeepers keep the both the ravens, and their secrets.
They sell baubles, which when broken will summon a raven from their tower to the holder, retrieve an item or message and return to the tower.
The Ravenkeepers' Oath ensures that the items will be passed on to those named in due time.
The Raven Lords hold the knowledge of how to create these baubles.
They often work closely with the Avowed Watchers and shared spaces with them.