呼神护卫为拉丁文Expecto Patronum的意译，是《哈利·波特》系列中守护神咒的咒语，用以抵御摄魂怪。发出此咒语时，魔法师需要集中精力，想着心中最快乐的事，口中念出“呼神护卫”。 咒语起作用时由魔杖末端喷射出银色气体，最终形成成型的银色动物守护神，每一个样子都不同，跟召唤它的巫师有关。
A Patronus is unique to the caster and is very personal. Incidentally, a Patronus will take on the same form as the caster’s Animagus.
Luna Lovegood is an incredibly talented witch. She's had some real darkness in her life (including the death of her mother ) yet she is an optimistic person by nature, so it will be easier to summon happy memories.
This fact, along with her skills as a magic wielder, results in her Patronus being more powerful than most. The free spirited hare is a perfect reflection of the character, who is both close with nature and easily underestimated.
Ginny Weasley is tough and determined. She's much like a horse in that she can be very calm and gentle, but also fearless and fierce in battle. Her own magical abilities mean that her Patronus is far more powerful than many of her peers.
Ginny has proven she can face off against great dark magic wielders such as Bellatrix Lestrange, demonstrating how much magic is fed into her Patronus. Many of her happy memories will come from a supporting and caring family, much like her father's Patronus.
Ron's patronus hound didn't get too many chances to stand out, though it was useful at times, of course. But the fact that it had a corporeal form says enough about it.
Being an Auror, and a member of the Order of the Phoenix, Tonks has had to rely on her Patronus wolf on more than one occasion. Her Patronus likely got the most use during Harry Potter and the Order of Phoenix – where she was helping to guard Hogwarts.
Her Patronus pulled double duty here, both protecting and sending messages. And frankly, there's no way that Mad-Eye Moody would have allowed her out into the field had she not been capable of defending herself.
Dumbledore is the only named character we know of with a magical creature as his Patronus. It likely has to do with his ties to Fawkes, and possibly even the deep ties his family has had with this special Phoenix. But we're just guessing there.
Dumbledore's Patronus was capable of sending off dozens of Dementors at once – This is enough to prove how powerful he is.
We have no doubt that Kingsley's Patronus Lynx would have been capable of facing off against several Dementor as well. It fits in well with Kingsley's attributes, for one thing.