The Circle

The Circle is a secret supernatural organization.

Description
Many adversaries of Harry Dresden, such as Grey Cloak and the Eebs, have mentioned The Circle. Dresden believes it to be a candidate for his hypothetical Black Council, though the Eebs may have referred to the Lords of Outer Night. Whether or not these two references refer to the same organization are unknown.

White Night
In White Night, Grey Cloak (Vittorio Malvora) mentions that Cowl is working for the Circle.

Speculation
In Changes, the Eebs mention the "Circle" by name, though this seems more likely to have referred to the Lords of Outer Night. Donar Vadderung referred to the Lords of Outer Night and the Red King's inner Circle.

Harry strongly suspects that Gregori Cristos is a member of the Circle, and that the murder of Aleron LaFortier was arranged to elevate Cristos to the Senior Council.

In Turn Coat, the Nevernever location that Wizard Peabody attempts to escape to after Morgan's trial is consistent with the description of the way that Cowl opens to the Nevernever in Dead Beat in order to flee Harry and the werewolves after the incident outside Bock Ordered Books. They are described as having "a strong smell of mildew and lightless/stagnant water," and in Turn Coat the way leads to a forest where the final struggle in the book takes place. Perhaps this is coincidence, or perhaps this location is important to the Circle.