Prejudiced and malicious to the bone, Death Eaters are the faction that make up Voldemort’s fanatical following. Fans of the Harry Potter film franchise became acquainted with these villains around the time of Harry Potter and the Goblet of Fire. The first sightings of this group in the films came during the scene where Harry and the Weasleys attend the Quidditch World Cup. After that, we see them performing various brazen criminal acts, as they work to do Voldemort’s bidding to take over the wizarding world.
We know the stories of Lucius Malfoy and Snape’s days as Death Eaters— but there’s a lot more to these hooded rebels than just being faithful followers to He Who Must Not Be Named. While the movies paint quite a picture of the Death Eaters, there are a few things that they have to leave out, or only touch upon.
The Knights of Walpurgis
Voldemort started his gang when he was largely still known as Tom Riddle. Way back during his days as a Hogwarts student, he assembled a group of classmates to discuss the politics of the wizarding world. It was during these school “club” meetings that Riddle’s dedicated following first started (audiences briefly see this young group in Harry Potter and the Half-Blood Prince during the Pensive scene).
According to J.K. Rowling, a potential name for this group in its early stages was the Knights of Walpurgis, which is a reference to Walpurgis Night-- a night in German folklore when witches and demons congregated. Some members continued to support Riddle’s ideals even after graduation, though there were some that disconnected from the group.
The First Wizarding War
The first Wizarding War is when Voldemort's intentions to overthrow the Muggle government and take over the wizarding world first sprung into life. With the Death Eaters by his side, Voldemort worked maliciously to murder Muggles, place spies within the Ministry of Magic, and capture and imprison "unworthy" wizards.
At the height of the first war, Snape tells Voldemort of the prophecy. What the movie neglects to mention is that the prophecy could have referred to one of two young wizards; Harry Potter or Neville Longbottom. Voldemort chose Harry as his equal because he had a Muggle ancestry, like himself. Of course, we all know the rest. Voldemort's powers were destroyed when he tried to kill Harry as a baby, and with his demise, many Death Eaters were captured and sent to Azkaban.
The Imperius Curse Claims
After the fall of Lord Voldemort, those who were found guilty of being a Death Eater worked viciously to counter these accusations. One of the most common excuses is that those who possessed the Dark Mark only worked at Voldemort’s behest under the Imperius Curse.
The Imperius Curse is Dark Magic used as a tool for a wizard to control another person's actions. In other words, many of the Death Eaters claimed they did not willingly support Voldemort. Death Eaters were able to evade imprisonment, under the false pretence that they were controlled by the Imperius Curse while they committed dastardly deeds. After all, as the fake Moody asks, "how do we sort out the liars?"
The Dark Mark
The Dark Mark was bestowed upon Death Eaters who were the most loyal to Voldemort. The skull and snake symbol was placed on the lower left arm of all of Voldemort’s senior followers. Besides being a communication system between the Dark Lord and his followers, he could also use it to track the whereabouts of his Death Eaters.
The Dark Mark was also placed above every house where the Death Eaters --or Voldemort himself-- committed a murder. Naturally, this mark evoked immediate fear throughout the wizarding world during the height of Voldemort's terror.
The 1994 Quidditch World Cup
The Dark Mark first appeared again during the 1994 Quidditch World Cup. Before its resurgence, we see Death Eaters hosting a march of terror at the event. However, once the Dark Park appears, a great majority of former Death Eaters fled the scene out of fear. Ron’s brother Bill even commented that the Death Eaters would be more afraid that he was back than everybody else.
Another event that isn’t presented in the movies happens during the Quidditch World Cup. The former Death Eaters did not simply make an appearance at the event. They were actually there torturing Muggles (the family of the Weasley's campsite manager), and it was Barty Crouch Junior who set off the Dark Mark above the event. It was the Death Eater's carelessness that incited Crouch's anger and urged him to cast the Dark Mark. His goal was not only to praise the Dark Lord's uprising, but to put the Death Eaters in their place.
Mysterious Members
We know that Draco Malfoy‘s father, Lucius, was one of the Death Eaters. But it’s not really made known that Crabbe and Goyle's (Draco‘s side cronies) parents were also Death Eaters, other than a casual name-drop in the graveyard. These two characters are highlighted primarily in Harry Potter and the Chamber of Secrets, and aren't really in the limelight in the movies after that. Both of Draco's friends followed in their father's footsteps, seeming to become Death Eaters during the Battle of Hogwarts.
Crabbe actually died by the effects of his own Fiendfyre curse after he set the Room of Requirement on Fire (it was Goyle who perished in the books, but the actor who played him wasn't available to film the scene). Igor Karkaroff, the Headmaster of Durmstrang Institute, was also a former Death Eater. We see him having an intimate conversation with Snape during the Yule Ball in Harry Potter and Goblet of Fire, because he was terrified that the Dark Mark was active again. Eventually, Igor was killed for his betrayal to Voldemort.
Bellatrix Lestrange
Perhaps the most sadistic of all the Death Eaters, Bellatrix ruthlessly fell into Voldemort’s regime right after graduating from Hogwarts. One of her most infamous crimes (and the one that sent her to Azkaban) was the torture of Neville Longbottom’s parents during the First Wizarding War.
What most people don’t know about Bellatrix (because it wasn’t in the movies) is that she had two sisters. We know of Narcissa Malfoy, Draco’s mother, but the two had a third sister— one who was banished from the Black family (oh, yes, Bellatrix is also Sirius’ cousin). Andromeda was ostracized from the Black family after marrying a Muggle-born by the name of Ted Tonks. The two would later have a daughter—Nymphadora Tonks, who was ultimately killed by Bellatrix in the Battle of Hogwarts.
The Muggle-Born Registration Commission
After the rise of Voldemort in 1997, he and his followers started the Muggle-Born Registration Commission. It was a method used by Death Eaters to find and persecute Muggle-borns. Under this registration, witches and wizards with Muggle (non-magical) parents were accused of having stolen their magic and were sent to Azkaban prison.
While we briefly see the registration in action in the movie adaptation, we don't understand the extent of what they're doing. We don't know that Pius Thicknesse was afflicted by the Imperius curse as Voldemort's 'puppet Minister,' either. This registration also dubbed Harry “Undesirable Number One,” with a 10,000 Galleon reward for his capture.
Professors at Hogwarts
After Dumbledore‘s death, Voldemort easily took over the magical realm and placed his Death Eaters in positions of power, both at the Ministry of Magic and even at Hogwarts.
Snape was named the Headmaster of Hogwarts during the 1997-1998 school year. During this time, students were required to prove their wizarding blood status. Two Death Eater siblings, the Carrows, became malicious professors at Hogwarts. Alecto Carrow reworked the Muggle Studies course to teach students of their superiority over non-magical people. Her brother, Amycus Carrow, took over the Defense Against the Dark Arts classes. Naturally, though, he changed the name of the class to 'Dark Arts,' and frequently taught students how to perform Unforgivable Curses.
The Rules
Someone as demanding and arrogant as Voldemort is going to demand his followers obey strict guidelines. Death Eaters are expected to adhere to certain rules, and failure to do so will result in some major consequences. These are more implied rules rather than written-in-stone rules. For instance, pledging as a Death Eater means that they are committed to the cause for life. There is no backing out.
Identity must be concealed with masks and robes, though a Death Eater must prove themselves loyal before they can officially claim this uniform. And of course, Death Eaters must be pure-blood, human (no werewolves generally allowed), and they must immediately Apparate to their master's side when they are summoned. Failure to comply or deny any of these demands can be fatal to Death Eaters.