Patronus Charm

From Hpwiki

Expecto Patronum is the incantation used to cast the Patronus Charm, a spell to repel Dementors and Lethifolds. You must keep a very strong happy memory in mind when casting. Most people can only conjure silvery mist. This form offers some protection as the attacker feeds from the mist, and not from the wizard directly. At full strength, the charm causes a silvery white mist-like animal -- a patronus -- to appear, which then chases off the offending Dementor(s) or Lethifold(s).

After a Quidditch accident Harry Potter asks Defence Against the Dark Arts Professor Remus Lupin to teach him how to conjure a Patronus. He learns quickly, and at the end of term this saves a few souls.

In the summer before his fifth year Harry is asked to a hearing at the Ministry for casting this spell in presence of a Muggle, his cousin Dudley.

The last meeting of Dumbledore's Army is devoted to practising this highly advanced spell.

A patronus can also be conjured for the purpose of relaying messages.

Word Origin: In Latin, expecto is to "I await, I desire, or I hope for" and patronus (patronum in accusative case) is "protector."