Kyrnil Long-Nose, a legendary Harbinger from the Second Era, began the tradition of trusted advisors called "The Circle". It was named after Ysgramor's council of captains. Its purpose was to serve as an example to the younger, newer Companions..
Over time the purpose of the Circle was somewhat subverted and it evolved to become a group where all members were secretly werewolves.
According to Kodlak's Journal, a previous Harbinger called Terrfyg was the one responsible for introducing the Companions to Lycanthropy. Terrfyg originally made a pact with the Glenmoril Witches that stated if the Companions hunted in the name of their lord, Hircine, they would be granted great power. They had not believed the change to be permanent, so the Companions were deceived. 
Kodlak Whitemane views the beastblood as a curse, and strives to cure himself and the other members, however many members of the Companions e.g. Skjor and Aela the Huntress view it as a blessing, and therefore the tradition has been maintained, much to Kodlak's distaste.
InteractionsEditSilver Hand are the enemies of the Circle, as their profession lies in hunting down werewolves with silver-made weapons. They are aware that the Circle is made up of lycanthropes and for that, they hunt and attempt to kill any member of The Circle.
The Circle meet at the Underforge (locked out until you have the option to join the circle), which is a small cavelike room underneath the Skyforge. The Underforge has a stone bowl in the center of the room, which The Circle uses to introduce the beastblood to new members. A small tunnel leads out of the Underforge to a farm outside of Whiterun. The Totems of Hircine are also found here after collecting them.
| Blood Oath|
Become a member of the Circle