User blog comment:DragonsHaveMoustaches/Why did Gaius take Morgause to the High Priestesses?/@comment-5102537-20120619113316/@comment-5209013-20120619181535

Thank you for your reply! I like your theory about the High Priestesses having foreseen the Great Purge. It sounds just like Merlin's tagline : 'you can't escape destiny' ; and that would mean the whole 'destiny-is-set-in-stone' element of the show doesn't only apply to Merlin but also to the other characters :).

But perhaps Morgause wasn't illegitimate as we actually don't know when she was smuggled out of Camelot. She might have been already a couple of years old ; we only know she said she'd been in Camelot when she was a baby and that Uther had wanted her dead at some point. Perhaps she had to flee from the Great Purge like many other magical children?

The High Priestesses were most likely very powerful, so they might have seen it as their duty to protect their fellow magic-users during the Great Purge (and therefore, destroy Uther's reign). Perhaps there were, like you said, always 'good' and 'bad' ones, but as the show is from Merlin's pov they are all being represented as evil :( ?