Lady Marinah Blackgard, is an unseen character in Game of Thrones. She is long deceased by the time the series begins and is therefore not expected to appear.
She was a member of House Blackgard and was the niece of Queen Meralith Blackgard who was married to Lord Torwyn Mercer. She was known for being extremely sexually deviant (alongside her husband) and was allegedly attracted to both men and women, and was known for frequently participating in orgies. For this reason she was known as both "Marinah the Deviant", and, derogatorily, "Marinah the Harlot". Despite her sexual behaviors and the contempt she received for it during her life, she is looked back on admirably today by modern-day memebers of Houses Blackgard and Mercer.