"Nope. Magic. It's usually a protective spell against these creatures we have called Dementors, they try to suck your soul out of you. All the happiness. So we use this to fight against them. It's a pretty advanced spell and you need to think of something happy for it to be of any use."
She looked at the doe and smiled again. It reminded her of home and, if she was honest, she was tempted to conjure the wispy animal so she could have some sort of link. Something to have with her. Yes, she had Remus, but Remus had his own life to lead and may not want to become her constant companion. Just having something or someone there would be nice.
"They can be used for other things sometimes, but that's their main purpose. Protection."