The Order of the Blood Moon, also known as Abaddon, was a dark coven, a group of evil witches that served Moloch. Their high priestess was Serilda of Abaddon 250 years ago, and rivals of Katrina Crane's coven, the Sisterhood of the Radiant Heart. They practiced black magic for malevolent purposes.
From 1712 to 1816, over a hundred witches of the Order were executed in Sleepy Hollow. They were then buried in the munition tunnels. During the Revolutionary War, the Order under Serilda had alligned with British. In that time they had attacked a camp near Albany, New York, leaving burnt corpses for the 37th Regiment. However, the Order then lost their high priestess Serilda when the leader of the Sisterhood of the Radiant Heart, Katrina Crane weakened her powers. Serilda was then burned at stake by Magistrate Robert Daniel Furth. Before dying, she vowed that the ashes of Furth's descendants would bring about her return.
In 2013, Moloch had his servant, Andy Brooks, bring Serilda back to life. Serilda then collected the ashes of Furth's descendants, Jeremy Furth and the last Hemmington. She was able to return to her full form, but obliterated by Ichabod Crane and Police Lieutnentant Abbie Mills. However, the explosion scattered her and other witches' ashes into a part of the Hudson River affecting people such Vivian Apfel, Hannah Schneider, and people at the Harvest Festival. They were possessed by the Order's witches. Luckily, Crane was able to clean the ashes off the people using a lightning to purge the people in the Hudson.
- Serilda of Abaddon (deceased, former high priestess)