Dark Mergana!
I am trying to find a story that I read a long time ago. It was about Merlin and Morgana being evil and them taking over Camelot. I believe that Morgause was also involve. It was about 20-30 chapters. Sorry about the vague description it been a really long time since I read it. If you cant find this story, then feel free to recommend me any stories that involve dark merlin and mergana.