Heartsbane is the ancestral Valyrian-steel greatsword of House Tarly of Horn Hill, borne by the Lord of Horn Hill for five hundred years. It is the only Valyrian blade still carried in the Reach.
By the events of A Game of Thrones it hangs at the hip of Lord Randyll Tarly, who is reckoned by many the finest battle commander south of the Neck. His firstborn son Samwell is, by Lord Randyll's measure, too soft to inherit the blade, and the question of who will carry Heartsbane after him is one of the few matters on which the lord of Horn Hill is openly uncertain.