Melisandre

Melisandre, often referred to as the Red Woman or the Red Witch, was a Red Priestess of R'hllor. Born into poverty in Asshai, she became a devout follower of the Lord of Light at an early age. She studied R'hllor and the magic thus provided for centuries on end, her physical health and appearance kept constant by an enchanted necklace. Just before the outbreak of the War of the Five Kings, she crossed the Narrow Sea to serve Stannis Baratheon, later aiding him in his campaign to take the Iron Throne, believing him to be the Prince that was Promised. Following Stannis's death, she revived Jon Snow and, now believing him to be the Prince that was Promised served him as an advisor until she was banished from the North. Melisandre eventually returned to Winterfell in order to fight the Army of the Dead. She perished during the ensuing battle in the Winterfell crypts, sacrificing herself to allow the defenceless occupants to escape.