Lyanna Stark was the younger sister of Eddard Stark and was betrothed to Robert Baratheon.
During the tourney of Harrenhal feast Rhaegar Targaryen, performed a sad and beautiful song that made Lyanna weep.
Rhaegar went on to win the tournament and shocked all present by passing over his wife to crown Lyanna, as queen of love and beauty. About a year later Lyanna was kidnapped by Rhaegar.
Robert believes that she was carried her off and raped her.Barristan Selmy is convinced that he her loved her and though that love sent thousands to their deaths.
Rhaegar spent much of the war at the Tower of Joy with Lyanna. He left to join the war effort and fought at the Trident, where Robert slew Rhaegar.
Ned rode to the Tower of Joy with his six companions and found the three remaining loyalist members of the Kingsguard guarding it. Only Ned and Howland Reed survived the ensuing battle. Ned found Lyanna inside the tower in a “bed of blood”, dying. Lyanna died in a room that smelled of “blood and roses”. She called for Ned to promise her something. When her brother gave his word, fear left her.
Neither the content of the promise nor the cause of her death are currently known. It is theorized that she died giving birth, possibly to Jon Snow.