Draco gave a small smile at the mention of his fox. He was proud of that spell as it had separated him from his parents. It also helped save him. "It's called a patronus charm. It's a shield used to protect you or others against dark creatures. And to a degree they can be used to send messages. The charm is different for every witch and wizard as it reveals a little bit of who you are personality wise.

However... the patronus charm is also light magic...good magic. Those who use the dark arts can't use the patronus charm due to the fact that in order to use the charm you need to use a strong happy memory to conjure it. Even for those who do use light magic it's a difficult charm to produce."