House of Cards

Silver has lived a hard life, her father was absent and her mother died when she was very young. She doesn't understand what's going on in her world, but all she does know is one thing--demons are bad and it's her duty to kill them.
Everything is normal until one day, Gale, her adopted father, makes her attend a gathering that the King had demanded all Slayers attend. At the gathering, she learns about who she is and what she has to do in order to survive.