"A Patronus is a kind of positive force, and for the wizard who can conjure one, it works something like a shield, with the Dementor feeding on it, rather than him. In order for it to work, you need to think of a memory. Not just any memory, a very happy memory, a very powerful memory… Allow it to fill you up…lose yourself in it…then speak the incantation ‘Expecto Patronum.’"
Ben Wessels as Remus Lupin in The Gathering Storm: A Marauders Fan Film.
Ben Wessels, who plays Remus Lupin in the upcoming fan film “The Gathering Storm”