Bellatrix- the crazy one. The torteress. Voldemort's right hand lady. She was not always like this. A duelist of her caliber could not have always traveled on the side of insanity. Once upon a time, she was Bellatrix Black. A girl beyond her years, with a wicked tongue and an even more wicked wand hand. She thrived on power. And with her uncle Orion and Aunt Walburga taking up all the money, she was stuck with the other side of power – knowledge. So the lonely girl studied. While Narcissa traded silly words with the blonde rat and Andromeda busied herself with the affairs of muggles, Bellatrix read everything from history to ethics to magic theory. But spells... Spells were where her interest lie. She learned every spell she could. She practiced every incantation until it was second nature. She poured over dueling and tactics guides. The most talented duelist of her age.
After she lost her mind, this talent was all she had left. So, she embraced it.