|Warning! This article contains spoilers. Proceed at your own risk.|
The Council of Sisters is a major antagonistic group introduced in Season 3 of the the Castlevania animated series. It is a sisterhood of powerful vampiresses which rules over Styria. It is commanded by the calculative vampire queen, Carmilla; with its headquarters established precisely at her castle in Austria.
Even though Carmilla has the title of the queen, according to Lenore they rule as a quartet.
One month after the battle of Braila, Carmilla and her vampire army finally return to their homeland, Styria, where she is greeted by Striga and Lenore, two members of Styria's ruling Council. They quickly notice that their queen has brought a new spoil of war: Hector, Dracula's former Devil Forgemaster, whom Carmilla orders to be immediately sent to the dungeons. Carmilla then enters her castle, declaring that she has a plan, and orders that a cartographer is sent to her chambers after her bath.
The three members of the Council: Morana, Striga and Lenore, meet later that night to hear Carmilla's new plan. Carmilla pulls out a map and begins to explain how Dracula's attack on mankind has rendered many of the nations surrounding Wallachia in complete disarray, giving a unique opportunity for Styria to expand to the east, in an area that she calls "the corridor", where the humans would be trapped and serve as cattle to the Styrian vampire army. While the other members of the Council initially express disbelief due to the lack of manpower to even sustain such borders, Carmilla quickly points out that Hector, as a Forgemaster, could be someone very useful to this regard. Morana, however, is still skeptical; given Carmilla's inhuman treatment to Hector, she doesn't see how they would be able to convince him to cooperate with such an operation. Recognizing this issue, Lenore offers herself to be the one who convinces Hector to work for them.
Soon after, Lenore arrives at Hector's cell. The Forgemaster is initially very distrusting of her, but eventually she manages to get through by giving him some measured human treatment and granting him access to some of the vampiric culture of Styria. After repeatedly visiting him and gaining his trust, Lenore seduces Hector and tricks him into swearing loyalty to her. She then puts a magical ring in his finger which bounds him to her.
When the members of the Council meet again, Lenore brings the enslaved Hector to the room, revealing that he is now her slave, and as such, his night creatures are now loyal to her. To ensure that Hector (and by extension, his night creatures) remain their loyal servants, Lenore hands over magic rings to all of her other "sisters". With the night creatures now under their command, the Council is finally ready to put in motion their plan to build their own empire.