User blog comment:Morganaforever/Morgana's torturer in 5x08/@comment-5204542-20121118150837/@comment-5674726-20121118152041

Arthur or Merlin, I'd say.

Arthur seems like the most probable option, if it's somebody who wants to make an alliance on the strength of their common hatred for Morgana, citing her two year imprisonment as proof that they can provide a valuable service when it comes to taking her out.