2. Dark Wizards Cannot Produce Patronuses
Warner Bros.The Patronus Charm is a very advanced piece of magic used to combat Dark creatures, most notably Dementors. As Dark wizards have an affinity for and are thus desensitized to Dark creatures like the aforementioned, they have no real need to produce Patronuses; and thats a good thing too, because they may not actually be capable of it. The widespread belief in the magical world is that no wizard that isnt pure of heart can produce a Patronus, corporeal or otherwise, but, while this is broadly true, some questionable wizards and witches (looking at you, Umbridge) have managed to cast the charm. This is due largely to the fact that the crucial ingredient of a Patronus Charm is pure happiness. Since Dark wizards are not capable of such purity of emotion, they also cant produce a Patronus. Double-double-agent Severus Snape was the only Death Eater who could, since he was redeemed by his love for Lily. An example to illustrate: the tale of the Dark wizard Raczidian, whose Patronus Charm backfired, causing him to be devoured by maggots. Lovely.