It is a general belief held by the wizarding world that only those who are pure of heart are able to cast Patronuses; this, however, is untrue, as several characters with negative personality traits are able to cast a fully-fledged Patronus. Although generally Dark witches and wizards will not try to produce a Patronus, not having any need for one, most Dark wizards will be devoured by maggots coming from their wand and consuming the caster.