The High Priestess is a card shrouded in mystery, much like Morgause and Nimueh. Despite their demise, we known next to nothing of their pasts, why they are who they are today. And despite how little is truly known about them, they play such tremendous parts in the lives of our heroes, Arthur and Merlin.

The High Priestess represents mysticism and knowledge, understanding of the arcane and gathering information and wisdom to be applied in real life, and in revealing hidden knowledge to the Fool as he goes about his journey.

Besides the fact they are literal High Priestesses of the Old Religion, Morgause and Nimueh have shown themselves to be well-learned in the arts and secrets of magic, and they both reveal pivotal information to the boys in their journeys, and even if that information was mostly false or manipulated, it still managed to change their lives forever.

I'm a little sad that both High Priestesses are characters that are evil in the show (and I feel the strong need to say that good or evil plays no part in the High Priestess as a card, or any card for that matter), but I have no intentions of changing these cards any time soon.

The Cards

02 - The High Priestess (Arthur)
02 - The High Priestess (Merlin)
02 - The High Priestess (Arthur: Morgause)
02 - The High Priestess (Merlin: Nimueh)

Morgause demonstrated to Arthur what kind of man he was by making him lay his head on a block and nearly axing it off, and then she revealed to Arthur that magic was involved in his birth, and that much of Uther's hatred of magic came from losing Ygraine's life for Arthur's. Arthur went charging back to Camelot and nearly killed Uther just to avenge what he saw was a great wrong done to his mother's memory and to the people of Camelot. While he now believes it all false, that doesn't change the catharsis that occurred between him and Uther, and it doesn't change how much he changed as a person as a result of Morgause's revelations to Arthur.

Nimueh manipulated Merlin about the poisoned chalice, and later on about sacrificing his life for Arthur's. It was her pushing at Merlin's strength that made Merlin develop from simply a boy trying to get his magic under control to a young man working for the greater good, ready to sacrifice his life for Arthur's. She manipulated Merlin with knowledge, but even then she changed his life and made him into a better sorcerer - and better man - through revelation and mysticism.