Merlin Season 1 Episode 13 : Le Morte d'Arthur
On a hunting trip, Arthur comes face to face with a creature of great power from the old religion. When Gaius informs them that it can only be killed by magic, Uther refuses to listen and sends out his knights to kill it. Arthur is fatally wounded and Merlin must go to the Isle of the Blessed to save him. But will he be able to pay the price?