The Mega Coven refers to an emerging community of witches that are intended to be successor of the now crippled Grand Coven. It was founded by Rowena with her newfound power after she mastered certain spells from the Book of the Damned.
It was later revealed that the Mega Coven never became a reality, as Rowena quickly abandoned this idea after Lucifer approached her.
In We Happy Few, it was later revealed that Clea, a former member of the Grand Coven and Rowena's ally later joined the "Coven" (technically "Witches' Den", as a Coven, according to Clea, requires at least three witches). After that, another 3 members, enlisted by Clea to help in God's plan to defeat The Darkness, joined it. However, all 4 members were later killed by Amara, making Rowena the sole member again.
Shortly after the events of Brother's Keeper, Rowena, with her new found power, attempted to recruit witches from the Grand Coven into her own. She tried to persuade them with the Book of the Damned; however, although many grunt level members of the Grand Coven were interested in the concept, the top members didn't believe she possessed it, leading to their deaths by Rowena's hand.
- Rowena MacLeod (founder)