Katie Cassidy ( otherwise known as Ruby) Is a reoccurring character in the series Supernatural.

Ruby is a demon who helps Sam get ready for the war thats coming. She was sent to protect him. She was a human once, but after she died as a witch, became a demon. Ruby later told Dean all of this. And also that Dean was going to hell...... and that there was no way to stop it. He had to find the courage somehow to not be a demon. Which Ruby says that he probrably will not.

Katie Cassidy:
Katie Cassidy was born November 26, 1986, In Los Angelus.
She is the daughter of the Pop Singer David Cassidy. As a child, Cassidy took tumbling and eventually became a cheerleader for the California Flyers. She cheered as A Freshman for Calabasas highschool. She graduated in 2005.
When Cassidy was in college she filmed in scenes of 'revenge of the nerds' but this production was halted when Agnes Scott College backed out. So instead she had a small role in "when a stranger calls", "click", and "sex, Love & secrets". Later she took on the role of a reoccuring character in "Supernatural".