Guinevere Jones, Season 1

[Gwen, Tasha and Morgana talking]

Morgana:
Hot blood and lack of sense. It was Guinevere's downfall, and because of her... Arthur's downfall too.

Gwen:
What are you talking about?

Morgana:
Care to translate?

Tasha:
Guinevere. She cheated on King Arthur with Lancelot. After that, everything went to pieces. Camelot tainted big time.

Morgana:
She made it so easy. I barely had to do more than put Lancelot in her path.

Tasha:
You put a spell on them?

Morgana:
To destroy Merlin, I had to first destroy Arthur.

Gwen:
But, you didn't destroy Merlin.

Morgana:
You will bend to my will, just as she did.