Lady Rosaline Mormont is a major character in Seaons 4, 5, and 6. She is a member of House Mormont of Bear Island, being the younger sister of Jeor and Maege Mormont, thus making her the aunt of Jorah Mormont. She served as the Mistress of Whisperers under Aerys II Targaryen, acting as Varys' immediate predecessor.
Like Varys, Lady Rosaline is a Targaryen loyalist, and is perhaps the strongest Targaryen supporter still in Westeros. She has been Varys' silent partner in aiding Daenerys Targaryen's campaigns in Essos. When Varys and Tyrion Lannister flee from King's Landing, Lady Rosaline acts as their lifeline to the goings-on of Westeros. Despite her loyalties to the Targaryens, as a noblewoman of the North, she was an on-and-off ally of Robb Stark during the War of the Five Kings, and later became a prominent advisor of Carmine Grayburn within Grayburn's Legion.