Harry Potter is iconic for a lot of reasons. The characters are amazing and will stay with you for years and even decades to come. The world-building is constantly being expanded, for better or for worse and whether we like it or not, so there will always be something new to discover. There's a brand new franchise in the same world thanks to Fantastic Beasts and Where to Find Them, again whether we like it or not. However, there's another reason why this franchise has stood the test of time and it's a reason we might not think of right away: the villains. Voldemort was larger than life on his own, but adding to that was the Death Eaters, who were evil and made for a compelling conflict, but also had lives and inner lives of their own.
The Death Eaters appear to go about things on their own, at least until Voldemort resurrects himself halfway through the series, but even before that, the Death Eaters were beholden to his will. They actually had way more rules than you'd even think of that they had to abide by to even get into the Death Eater squad, let alone stay in Voldemort's good graces. I went back through all seven books and all eight movies and pieced together what I think the Death Eater rule book is, and here are 25 rules they have to abide by or be the exception to that rule for.
If you're a Death Eater in Voldy's inner circle, you absolutely have to have a Dark Mark. There are exceptions to this rule, though, so your mileage may vary depending on how clever you are and how good you are at feigning loyalty. For example, Narcissa Malfoy never took the Dark Mark, despite the fact that her husband and sister and eventually her son all took the Mark for themselves. That being said, not everyone is Marcissa Malfoy and the only reason she was able to get away with that was because she was better at Occulmency than Snape.
If the Dark Lord Voldy slips into your DMs and you leave him on read, he will literally destroy you or put you in a position to be destroyed. When Voldemort called the Death Eaters to show up for him on the day he got his body back, he had a lot to say about the people who were less than hesitant to show up for him. A good example of someone who tried ignoring Voldy's call to action was Igor Karkaroff, the headmaster of Durmstrang. He spent a good amount of the Goblet of Fire freaking out about his Dark Mark to Snape and he did not meet a nice fate after ignoring him.
If you're a Death Eater, snitches get stitches. You can't snitch on any one of your evil buddies, even if it means you get out of trouble. Voldemort was a Slytherin, as were a lot of our named Death Eaters. Slytherins aren't evil as a rule, but they do value personal loyalty, even the evil Slytherins like the Death Eaters. That means that the Death Eaters actually do see themselves like a family, the way a gang or a cult would. This means that anybody crossing the line and spilling the beans to outsiders is turning their back on their family, and Voldy doesn't take kindly to that. Neither do the other Death Eaters, for that matter.
The Death Eaters come from overwhelmingly pureblood families, which doesn't really mean anything in the grand scheme of things. However, unlike other pureblood families like James Potter's parents and the Weasleys, the Death Eaters are actually very invested in keeping the blood lines pure, so they will only marry other purebloods. Considering the lack of new blood in Death Eater circles, this means that their family trees are all starting to come together, making every future marriage inch closer and closer to incest. Canonically, the Weasleys, Malfoys, and Blacks all share blood ties.
Should a member of any Death Eater family choose not to partake in the almost Targaryen-esque family line-blurring going on, they're also considered blood-traitors the way the Weasleys and Potters were considered blood traitors. For example, Narcissa Malfoy and Bellatrix Lestrange had a sister, Andromeda, who stepped out on her family of origin after falling in love with a Muggle, Ted Tonks. Sirius Black also stepped out on his biological family after being accepted as a son to the Potters. Both of them were literally burned off their family tree at Grimmauld Place for their trouble.
As a Death Eater, you're basically making an investment for the whole family because if anyone in the family tries leaving the fold, they're basically stepping out on Voldemort and that's a way to get yourself in hot water. When families like the Blacks and the Malfoys joined up with Voldemort, they went in with the knowledge that their children were going to grow up to join Voldemort as well, because even if they didn't want to, they'd have to in order to stay alive. This is the whole reason Draco got recruited to execute Dumbledore in the first place: Voldemort did it to solidify the Malfoy family's loyalty.
The Death Eaters are like a real life gang, blood in, blood out. When you're in, you're in for life. This is why even if Peter Pettigrew wanted to renounce Voldemort and repent for his betrayal of James and Lily Potter, he wouldn't have been able to because Voldemort and the Death Eaters would have gone out of their way to put him down. Even Severus Snape, who defected from the Death Eaters in spirit and hadn't been part of them in truth in years, couldn't actually, publicly leave because that would have sealed his fate and condemned him to death. Ironically, both Peter and Snape were eliminated by Voldemort, at least by proxy, probably because of their secret rebellion.
If you're a Death Eater, your blood has to be pure in more ways than one. Essentially, if you're not purely human, you can't be a Death Eater. This excludes at least one of Voldemort's biggest supporters and most loyal followers, Fenrir Greyback. Greyback is a werewolf who coincidentally was the person who gave Remus the werewolf virus, but he also went on to disfigure Bill Weasley and attack Lavender Brown. This rule of Voldemorts would have also excluded half-giants like Hagrid (who he blamed for the Chamber of Secrets as a teenager) and half-veela like Fleur Delacour.
Death Eaters can have ambition, but they definitely can't try and surpass Voldy himself. Basically, they can't try and take more initiative or do things outside of Voldemort's purview. A good example of someone who tried to do this was Snape. He basically acted like he was less expendable than he actually was and got rewarded by a fatal snake bite. Other Death Eaters who got a little too big for their britches were Lucius Malfoy and Bellatrix Lestrange, both of whom thought they were much more vital than they were and that Voldemort actually cared about their contributions. Lucius lived, but he definitely paid for that arrogance, and Bellatrix ended up six feet under.
While Voldy does love a good Forbidden Curse, he doesn't make destroying someone a requirement to join his ranks. However, if Voldemort says you have to eliminate someone, you have to do it or else. A good example of that is when Voldemort said that Draco had to be the one to end Dumbledore. Snape ended up being the one to do it and thankfully Draco got to live to the end of the series and onward into the Cursed Child, but before that, Snape hadn't had to hurt anyone in order to be a Death Eater. On top of that, Snape only eliminated Dumbledore because Dumbledore told him to, so had Draco not been involved, Snape wouldn't have had to hurt anyone at all!.
Death Eaters, more often than not, come from Slytherin, but that isn't to say that Slytherin is entirely evil. You might think that the Death Eaters are a snakes only club, but that couldn't be further from the truth. The one thing Voldy won't discriminate against you for is your Hogwarts house. A lot of Death Eaters don't have a designated Hogwarts house, and several prominent Death Eaters were claimed for other houses. Peter Pettigrew, for example, was a Gryffindor, while Igor Karkaroff was from Durmstrang and had whatever house he was from at that school.
Death Eaters go everywhere in style. Too bad their style is less haute couture and more "hate couture." Death Eaters, when they're out and about and being evil, don't wear normal clothes, they wear creepy black robes to go with their ornate but very creepy masks. Basically, the goal is to look scary and threatening, but also fabulous. Too bad for Voldemort that the Death Eaters basically stunt on him in the outfit department because while they're wearing creepy designer masks, Voldy just has his weird, snakelike face, so he looks less scary and intimidating by comparison.
Death Eaters wear masks when they go out to do their evil deeds. There's a reason for this: Voldemort picks people for his inner circle that have power and that are pillars of the very system he's trying to bring down. That means that Death Eaters wield a lot of power in their secret identities and that would be jeopardized if they were known to go cavorting around with the Dark Lord. To be fair, this seems like a rule the Death Eaters created themselves, not Voldy, specifically because Voldemort doesn't seem to care enough about his followers maintaining their power.
There's a difference between being a follower of Voldy and being a Death Eater. For example, the Slytherin kids in book six who were basically emulating their parents were just wannabe followers of Voldemort who weren't in the inner circle. However, Draco Malfoy was raised above those kids and got the Dark Mark and Death Eater robes, making him a Death Eater in earnest, at least for a while. Basically, you wait your turn for your time to get into Voldemort's inner circle. If you wait longer than someone else does to get in, that's too bad because Voldy never said life as a Death Eater was fair.
Many people who follow the Dark Lord wait a long time to get into his inner circle and to call themselves a Death Eater. However, a lot of those people never actually got to become a Death Eater themselves. For example, despite Fenrir Greyback's faithful service to Voldy, he never received the robes and Mark because of his werewolf heritage. If you were passed over, you can't complain about getting passed over. That would essentially be like complaining that you didn't get promoted to your boss right after you were passed up for a promotion, except your boss is a wizard dictator. Not a good move.
The people who come from families who follow Voldy tend to be families with a lot of power and who are deeply entrenched in the wizarding world and the existing system. Most notably, these families have a huge amount of money. They're essentially the people who would be on My Super Wizard Sweet Sixteen if that were a thing in the wizarding world. In order to be a Death Eater, you have to have money, or at least power. It's why Voldemort probably wouldn't have gone after the Weasleys as followers anyway even if they'd wanted to roll with him: they didn't have the financial capital for it.
Speaking of money and power, the money is a side effect of the power when it comes to Death Eaters. In the wizarding world, the Death Eater families like the Malfoys, Blacks, Lestranges, and others are either huge socialite families with a lot of connections, members of the governing body, or both. Voldemort basically knew exactly who to target and who to recruit when building his armies. He also made sure future generations of those families would be bound to him barring a few outliers: to reject Voldy would mean to get ostracized from the whole family as Sirius and Andromeda did.
Death Eaters have different ways of reaching each other. There are the more traditional, mainstream ways to get in touch, like Apparating, the Portkeys and going through the Floo network. There's also the mail: sending an Owl brings two people together pretty quickly in the wizarding world. However, Death Eaters have another way to get a message out quickly: using their Dark Marks and casting a specific spell that blasts the Dark Mark into the sky, not unlike a Bat-symbol. Basically, when you see a Dark Mark in the sky, that's your cue to drop everything and check in with Lord Voldy.
Death Eaters can't use Voldemort's name in any context. Let's be real though, with the exception of maybe three people, nobody was using Voldy's name. Harry and Dumbledore alone used Voldemort's name consistently, and while others like Hermione and Lupin have said his name before, most people were calling him You-Know-Who and He-Who-Must-Not-Be-Named. Death Eaters, however, have to call him the Dark Lord. Calling him anything else basically lets people know that you're not loyal to Voldemort, at least in the evil wizard circles.
If you're a Death Eater, you accept whatever Voldemort gives you. He could reward you as he did with the Malfoys and Bellatrix Lestrange by giving them a seat at his table and making them trusted lieutenants of sorts. However, with the rewards come the punishments and if you're a Death Eater, you have to be cool with that too. For example, when Voldemort made Draco the one to eliminate Dumbledore, he didn't do that for Draco, he did that to punish Lucius, his father. Peter Pettigrew was also sort of punished for his betrayal of the Potter family (which worked out in Voldy's favor but Slytherins are about personal loyalty so I think Voldemort would have hated what Pettigrew did) by getting his hand cut off.
Yes, you want your friends to be super skilled and awesome, but let's be real: not everyone is going to be the best at everything and if you exclude someone based on their perceived skill, you'd be mean for that. Death Eaters don't really care about where someone is from and how good they are at magic because what's uniting this crew isn't skill, it's devotion to a cause. For example, people could have looked down on Peter Pettigrew for being beneath them, but they didn't because he was one of them. That being said, Peter Pettigrew managed to become an illegal Animagus as a teenager and helped create the coolest map in all of fiction, so dismissing him is just dumb in general. I don't like him either, guys, but it's true: Peter Pettigrew was a low-key beast.
When you're with Voldemort, it's blood in, blood out, like we've already discussed. That means that when things get dicey or the plan falls through, you need to take your lumps and represent Voldemort and not try and weasel your way out of trouble. Many Death Eaters broke this rule when Voldemort lost to baby Harry, which ended up biting them later when they came back to serve Voldemort when he came back. For example, the Malfoys went back to a normal life and acted like they didn't have anything to do with it. On the flip side, Bellatrix Lestrange and Barty Crouch Jr. were ride or die for Voldemort and paid for it in mainstream society, but they didn't break that rule.
It's not just about loyalty when things go bad, however. If you're a Death Eater, you can take off the cloak and reenter modern, mainstream society if you want, but if you're asked whether you're loyal to Voldemort, you can't really say that you aren't. To be fair, you can dodge the question, which is how so many pureblood families who traditionally end up in Slytherin have a hard time getting the Voldy stink off of them. However, this rule is more for other Death Eaters in dealing with each other because Voldy knows who you are if you're with him.
Death Eaters have to deal with a lot of contradictory rules because while they can't deny serving Voldemort and agreeing with his cause, they can't lose their place in mainstream society either because that cuts Voldy off from mainstream resources, like being able to move through the Ministry with few issues and use the wizarding bank without everyone being like "hey, it's that servant of Voldemort." Long story short, Death Eaters have to walk a fine, fine line between outward appearances and inner loyalty. To be fair, that's probably why Voldemort chose to recruit from the Slytherins because that's a skill good and evil Slytherins have in spades.
The biggest rule of all when it comes to being a Death Eater is that nobody touches the Chosen One. Voldemort chose to go himself to take down two 21-year-olds and their infant son because that was the Chosen One and in Voldemort's mind, it had to be him to do that. Had Peter Pettigrew chosen to destroy the Potter family himself, he would have paid dearly for it because that was Voldemort's fight. Had the Death Eaters taken Harry out at any point, it would have been a major problem, even if the Death Eaters had actually succeeded, because Voldemort would have felt robbed of that opportunity. Even if it would have been better for someone else to just take the Potters out, it would have been an issue and they would get punished for it. This is where I have to mention a secret rule Death Eaters know but can never acknowledge: Voldemort sometimes does dumb things and you have to just roll with it.