Serena thought carefully about a happy thought that could produce a Patronus. Then concentrating exclaimed, "Expecto Patronum!" Suddenly there appeared a silver mist extending from her wand tip that formed into what was now the familiar lion she had come to admire. Even though it wasn't as sharp an image as she wanted, it was still clearly visible. "It took me two years, and a lot of practice to be able form my patronus. I hope it doesn't take as long for me to strengthen it. I've never had to use my Patronus to protect me, but I'm sure it's strong enough for that."