Aemond Targaryen

She was born into a family of modest means but respected warriors. Her mother died when she was born, and the girl was raised by her father—a stern man with calloused palms and a kind heart, who didn't discriminate between sons and daughters. But he died in the war, leaving his daughter in the care of his faithful friend, Ser Kristan.
Thus, she found herself in the state's main castle. The chief of the guard, remembering his old friendship with her father, accepted the girl without further ado and began training her alongside the other students. The noblewomen grimaced at the sight of a girl with a sword and whispered behind her back. But she quickly proved that her place was in the training yard, not in their embroidered chambers. Every strike of her blade was her answer to their taunts.
She wore the mask for two reasons. First, it concealed an ugly scar that ran from her temple to her chin—a reminder of the night she first picked up a sword. And second, she was tired of hearing whispers about her "mannish" appearance. She was practicing her strikes with Simon today, on a day when the ruler's two sons were practicing on the adjacent court. She tried to ignore them—the princes were otherworldly creatures to her, unattainable and alien. But out of the corner of her eye, she noticed the younger of them looking at her. She didn't pay it any mind. After all, she wasn't a lady for a prince to take a serious interest in her.
After training, he approached her mentor. The girl heard their conversation but didn't turn around, pretending to be busy sharpening her blade.
"Who is this girl?" he asked Kristan, curiosity evident in his voice. "I've never seen her before. And why is she wearing a mask?"
"The daughter of my fallen friend," the mentor replied. "I took her in for training at his last will."

• And I never noticed her?
  He fell silent, and she felt his gaze on her back.
  "Does she... always wear a mask?" the prince asked.
  The mentor shrugged and glanced briefly in her direction.
  “I think it would be better for you to approach her yourself and ask after training.”

She was born into a poor but respected family, a minor lord in the Riverlands. Her father, Ser Roland Blackwood (a distant relative of the main Blackwood family), was a loyal friend and comrade of Ser Criston Cole, dating back to their days together in the Kingsguard. Her mother died in childbirth, so she was raised by her father—a stern but loving warrior who saw no difference between his son and daughter. He taught her swordsmanship from the age of five, telling her, "In this world, women need steel as much as men—if not more." Her childhood was spent in camps, garrisons, and camp tents. She knew no courtly manners, dancing, or embroidery—instead, she learned to clean chainmail, pitch a tent, and judge the direction of the wind by the smell of smoke. By the age of ten, she could already give many squires a run for their money, and her father was proud of her, dreaming of her one day serving some lord as a bodyguard or captain of the guard. When yet another civil war broke out in the Riverlands, Ser Roland was called to war. He left you in the care of an old armorer at the castle, promising to return in two moons. But the war dragged on, and six months later, a messenger came to you: her father had died in an ambush while covering the retreat of his men. Before he died, he managed to give the messenger a letter with one request: "Take my daughter to Ser Cristo n Kol in King's Landing. Tell him I repay my old debt to him. Let him take care of her."