The impoverished Lord Maegor Towers lived in the Tower of Dread, leaving the other towers empty. King Jaehaerys I Targaryen settled his widowed sister, Queen Rhaena Targaryen, in Harrenhal in 56 AC. Rhaena, who lived in the Widow's Tower, became friends with poor Maegor, and she took care of his household after their lord's passing in 61 AC.
A Clash of Kings
While Lord Tywin Lannister holds the castle, the Brave Companions, a sellsword company from the Free Cities, are housed within the Widow's Tower. When the Brave Companions return with captured northmen and rivermen, Ser Amory Lorch has the prisoners taken to the dungeon beneath the tower. During the fall of Harrenhal, the captives are freed by Jaqen H'ghar, Rorge, and Biter.