So I'm starting to develop an idea for a campaign in which the PCs join a guild that sends adventurer's to different planes to go on various quests. Go to the Feywild to rescue someone who was kidnapped by fairies, go to the Shadowfell to root out the source of undead corruption, go to the Plane of Air to bring back an artifact, etc. The guild would have a patron who doesn't actually run anything but basically payrolls the whole project and so has a lot of influence in their activities.

My idea is that the patron of this guild is the villian, or at least a villain. My thoughts so far is that he's either just a greedy person who wants the party to steal valuable items for other planes so he can sell them to collectors, and as time goes on the quests become more morally dubious until the party has to decide if they're going to do these evil jobs or say no to the patron (for example, he may start out wanting them to collect art pieces from other planes to sell, then it escalates to stealing magic artifacts that would destabilize innocent societies if lost). My other idea is that he's a green dragon in disguise using the party to collect things for its horde.

I could make him some bigger bad, like he's collecting artifacts from every plane to make a powerful McGuffin to take over the world yada yada. Just not sure where to take this idea.

So any brainstorming help would be appreciated!

If you want monsters that actually have motivation to try and corrupt PCs, I suggest fiends, though you'll have to homebrew stuff (skills, possession or shapeshifting) -- while canonically devils are supposed to be interested in corrupting humans, most of them neither have abilities that let them pass among humans, nor any skill with deception, and the same for demons that are supposed to be interested in that stuff, like the Glabrezu, though you can use an Arcanaloth without any changes.

If you want that nobleperson to really be a BBE they will remember, then don’t create them as a “villain” at all. Create them as a hero/heroine who is prepared to do things other people wouldn’t conceive of in order to achieve their “noble” goal.

In DC Comics, one of Batman’s enemies is a man named Victor Freeze. He was willing to steal, kill, and even die to save his beloved wife from her frigid prison. After she was proven to no longer “savable,” he became a man willing to steak, kill, or even die to see that her murderer be punished.

In the Pixar movie, The Incredibles, a boy named Buddy Pine wanted nothing more than to be a superhero. That was, until he was rejected, belittled, denigrated, and trivialized by the most “super” of heroes. He vowed to ensure that normal people would never be the victims of those “so called” heroes ever again. And after he had eliminated those responsible for his suffering, he would make his technology available to everyone. Because, in his words, “if everyone is ‘super,’ then no one is.“

Heck, even Hitler genuinely believed he was doing the world a favor.

Don’t make a “villain,” make a “hero” so broken that the world sees them as evil… but not until act 3. 😉

Strahd is a great example of a villain that’s somewhat relatable or rather one that’s familiar. 

The above person is right about how the villain sees themselves. The villain is the hero who uses any means possible, including murder, extortion and deception. 

I have this Villain archetype I used to use, the “Disinterested Never do well Noble” which is the most interesting person at the party. Along the lines of Johnny Depp, the Libertine. 

This villain has a quip for every occasion and is actually sympathetic to some odd causes, dogs, cats, maybe even the poor. However, he’s (or she, needs depending) isn’t above sacrificing those things to a Greater Devil to torture for eternity to accomplish their goals. Those goals being supremely selfish, such as eternal life, the power to destroy an enemy, and perfect cuticles, even after carving the heart out of a sacrifice with a jagged piece of obsidian. 

Then host a dinner party. 

What I accomplish with this is a sort of character shorthand, I can bring this one in, see if my players vibe to it, then move on if they don’t. 

I’d advise put together a few such archetype villains and see how your party reacts, give them space and see what they like.

I would recommend reading/watching The Count of Monte Cristo to find a most spectacular evil noble villain.  It might not fit your needs, but it is a great story and full of inspiration for D&D shenanigans.

The Victor Freeze example where the man is causing great harm to save his wife is an example.  Or you could have a man raising the dead but he's using them to run farms because the people are falling sick and he's using the dead to help keep the living alive.  With each wight the party kills, less food is gathered and more die.  It could be a Gold Dragon locked in the form of a human who is using the party to gather the components to get him back to being a gold dragon but at the cost of the ecology and treasure of the area they plunder leading to poverty and destitution for those the party visits.

To follow up some of the recommendations, I'd actually use Bruce Wayne/Batman as your bad guy.  It's been done in actual comics and animation.  His fortune can bankroll a lot and gets his hands in a lot of things.  He's very accustomed to having things done his way, almost dependently so.  He's a very paranoid personality and anyone he's worked closely with for a long time ... he's got a file with a half dozen meticulously planned out ways to take each party member down.  

you may find a googly of the term "Robber Baron" gives some inspiration

One option is to keep the ends "good" and the means "Bad", and then have the NPC neglect or avoid going into details of their plan.

I am running/writing a module in which an artificer with a tragic backstory is seeking help to complete a device which will cure lycanthropy. Her backstory is that she was a werewolf, and that her son contracted it at birth. When he was killed by monster hunters, she vowed to find a way to end lycanthropy, and she even transferred her soul into a warforged body to escape the curse. Her experiment had her ejected from the artificers guild, saying that she had gone too far and become obsessed. She is having the party collect the items she needs to complete the device, after they brought her a magic box which was a key part of her device, and that she had thought lost forever. She is helpful, polite, friendly, eccentric, and gives off every indication of being sane, rational and above all, good. 

You could rip Mercer Frey from the Elder Scrolls Skyrim, here's the wiki on him so as not to spoil it...

https://elderscrolls.fandom.com/wiki/Mercer_Frey

The character that immediately came to mind for me when thinking of a good villain who is a noble is Cersei Lannister, from Game of Thrones. Her power stems purely from control and influence over others (as compared to someone who had physical prowess or magic abilities). Check out this clip: https://www.youtube.com/watch?v=zdRJybJ047I Could be good inspiration!

First up, I like the idea, in theoretical terms. In a novel, this would make a lot of sense. But I fear that it ultimately doesn't work for a D&D campaign because it requires the PCs to blindly do what the Noble wants for at least a period of time without having any real say in where they go, what they do, and I don't see much way for a character to personally invest into doing these tasks outside of getting paid for them.

Potential issues that I see with this as a campaign concept (there is nothing wrong with the character concept):

• The description you've given indicates that the PCs are going to be constantly working for the BBEG, unknowingly. A large part of the campaign will be built around doing bad things, when the players may well want to play Good alignments.
• The campaign requires them to undertake missions not because they are personally invested in them, but because they are being issued by someone else, whom the DM has to effectively tell them "You want to work for X." There's an unspoken agreement in D&D that the players will find reasons to do the things that the DM is prodding them towards, but this has further complications here.
• The PCs could decide that they won't play ball and steal the items very early on
• You could find that if the PCs are dedicated to working for the Noble, then they may never care that the Noble's goals are wrong
• If there is an overarching plot across all the adventures, the PCs are effectively the bad guys: I know that for my players, realising late on that they are actually the villains would leave a very bad taste in their mouth
• It's extremely hard to pull off sending the PCs to do something that's morally wrong without them noticing it. If stealing the item will destabilise a peaceful nation or leave an innocent town defenceless, either (a) you disguise it so well that they won't know or (b) they'll know, and choose to do it anyway
• After a long time serving this Noble, they may simply not care that the Noble is the BBEG 

So to demonstrate it through two opposite character examples, these are two potential problems that I'd have playing in a campaign that ran like this:

1) Character - Hal the Mercenary. I create a mercenary sorcerer called Hal. From Session 0 I understand that we'll be getting paid to undertake retrieval missions from a noble. Hal is True Neutral. He wants to earn money because he loves the finer things in life and was poor when he was younger. As the missions become more morally dubious... Hal doesn't care at all. In fact, he doesn't even see the Noble as a villain. He's worked for him from level 1 to level 10 when the reveal happens, and actually he just shrugs and says "Sounds like I've done much worse than that. Can hardly claim I'm not just as culpable now, can I?" To Hal, the Noble is not a villain at all.

2) Character - Hal the Worthy. I create a sorcerer called Hal, who needs the money to pay for magical medicine for his sister who needs constant medical attention. Hal is happy at level 1 going into a spidery cave to locate a gem of power. But at level 3 when the party is sent to steal from a Feywild noble, Hal shakes his head and says no. He needs the money to save his sister, but there are other ways to earn it, and she'd hate if the money came from there. Hal refuses to work with the noble from that point.

Now, I'm not saying that this campaign concept cannot work, but it's a hard one to pull off and you'd have to be 100% certain that when the moment of reveal comes and the players learn that the BBEG has been duping them all along, they don't feel like all the levels of adventure before that were things that they wished they had not done. Your players are going to be culpable as part of the crime spree. They are henchmen to the BBEG. They didn't invest into those adventures because they wanted to help so much as because that was how the adventures were set. You ultimately need to know that at the moment when they work out that the BBEG had a bigger plan all along, that they don't become annoyed that they've been duped into being the bad guys in a way that means that they could never have known it before you drop the hammer.

Sanvael has some good points, though I feel that a well designed villain would not have these tasks seem evil. They might even be tasks which would have been good, were it not for them being for the Noble. For example - the Noble tells you of a cult who are trying to summon a powerful demon. They are using an artefact to do it. The Noble convinces the party not to trust the constabulary or the local temples as the cult has members everywhere - so go in there, get the artefact, and bring it to him, where he can put it in his vault to keep safe, and find out how to turn the key the othjer way and lock the doors for this demon forever.

Some of this is the truth - the cult is trying to summon a demon using the artefact, and does have members everywhere. But, the noble doesn't want to keep it safe - he wants to use it for his own ends. So the mission they are sent on is in fact a good one - but it will put the artefact in worse hands.

For the two characters, there is a key tipping point in this sort of thing where the BBEG will stop trusting them, or consider them too great a threat, and will try to dispose of them.

If the characters decide to stop working for him, they know too much and must be killed, possibly interrogated if they were halfway through a mission so the BBEG knows what they did. This will progress the plot naturally, and is to be expected - for the BBEG to be evil, they will need to turn on the good guys at some point. 

If the characters go along with it all, completely duped, then the BBEG might decide to send them on a death mission. Maybe they succeed, or perhaps the ancient dragon they are sent to kill has been watching them and knows the truth. Either way, the plot progresses.

If the characters knowingly go along with it, then the BBEG's plans succeed. The party becomes an evil party, and you can decide whether to continue as an evil party of start a new campaign. again, the plot progresses.

The important thing is to lay the story behind the players, not in front of them. the BBEG wants to use the PC's to get stuff and enact their plan, and will try to trick them into doing it. Meanwhile, a good dragon watches and waits for the perfect time to intervene for the heroes. Everyone has a way they want the story to go, but nothing is pre-ordained (unless, you know, there's a prophecy or something!)

Now whatever happens, you have this basis, and can build from it - build foundations, not goalposts. set the starting conditions and see if the players go along with it, or if they smell the rat straight away. But don't set a goal for the players to do X missions for them before it becomes apparent - set up the missions and give yourself an idea of what to do if they work it out at each stage - IE, what does each artefact/mission mean for the BBEG?

In my game, I have a few key things which I need the party to gather for the BBEG, which will allow her plans to come to fruition. Each mission features a higher chance of the truth being revealed - the first few are inconsequential, but then it's things like stealing from the guild of artificers who she was kicked out of, who may catch the party and ask why they were taking it, and so reveal what the artefact does and why she was kicked out, which will be the big reveal for the game. 

If the party figure it out early, have the BBEG disappear, and more of the retrieve missions keep happening - the missions the party go on all seem to have been triggered by a theft (a rampaging giant who's been stolen from, for example), so they know the BBEG is still going in the background!

Reading this, my mind went back to the first Fable game, with Maze as one of the primary villains. Maze is there at the beginning, makes your introductions, starts you up in training, but then, though he's the head of the guild, he's mostly out and about doing things and you as the player mostly work with an old man known as The Guildmaster, who's sort of upper-middle management. The guildmaster trains you, oversees your missions, etc, and you run into Maze every now and again while he stops by to give you information on the main quest, but then as the game progresses, it turns out he's in league with the guy who torched your hometown and presumably killed your family. 

Idk exactly how you'd implement it into your campaign, but there could be enough story parallels there to look back at the game for inspiration. 

ooh, +1 for having the bad guy betraying not only the party, but also the person the party is dealing with. That removes the risks of the party just killing/jailing the guy they're dealing with when they work it out!

I just wanted to chime in that I think you've gotten a lot of really good suggestions for how to write this character's motivation, but I think their actual goal and how they intend to accomplish it should be hammered out... whether it's a noble goal like rescuing a loved one or a selfish goal like becoming richer, etc.

The important part is that he arranges for the players to be sent to various locations in a manner that does his bidding... what I would do in that situation is making it a running theme that he's sending the party to these various planes to steal artifacts that can be combined together in some way to accomplish their goals. This is a fairly simple concept to implement... let the party believe that they're just a recovery team, gathering cursed or otherwise dangerous objects, with the intent being to protect the world from these powerful artifacts. Most players will go along with this concept without question... just make sure that the first few items they're sent to recover don't appear to have any practical use for a group of adventurers, so they won't feel tempted to just keep them for themselves.

One thing I would also suggest introducing is having the items "destroyed" by some big arcane device, like a forge or something. Really the objects just fall through a chute or something, but the forge would give the impression that the objects are truly gone and will set up the players to being surprised when they return in some way. Maybe also have the forge output rewards of some kind... like magical crystals the players can use, so they'll feel motivated to continue to destroy these objects because there's an obvious, tangible reward that's more useful to them than a magical object that doesn't have obvious practical applications.

The question I would ask is "What do you think is interesting?"

From a writing perspective, I would say find an issue you have and have something to say about and then create a character around that trait as their central theme. A good, interesting character should have clear (to you) motivations that inform their actions. Maybe the nobleman is acting out of pride. Maybe his actions are motivated by this fear of disgrace and acquiring greater and greater items, regardless at the cost to others, is justified in his mind because it keeps him, who is operating under the terrible weight of his family's legacy, from dishonouring himself before his ancestors and society. It's almost not even something he's consciously doing; it's more like a hunger. He needs this. But soon as he gets one of these fantastic items, it turns to ash in his mouth. The hunger is back before he realises it.

Interesting people are other people we can relate to. It's horrifyingly egotistical, but alas. So, if you want to make a person that people want to learn more about, make him a believable person: someone you could forsee yourself becoming, under awful circumstances.

One adventure this reminds me of was when I had a Player make a character that he wanted to be a sort of Sherlock Holmes. Okay, cool. Sherlock needs a Moriarty, though.

So the campaign unfolds, adventure 1, a dead clockmaker and all of his apprentices are dead, except one, who is missing. There’s a clue that leads him to our next adventure, session #2, a warehouse full of explosive powder leftover from the war (it was a campaign loosely based in 1820’s Denmark, but with magic) the clue from here leads to session #3, a museum flyer that advertises a unique exhibit, an elder dragons skull. 

So what does my Sherlock do? He misses the point of all the clues, (clock, explosives, valuable object) and decides to run at a right angle to that plot line. Moriarty still blows up the museum, steals the dragon skull, and frames our dear Sherlock for the whole thing. 

I often flip this adventure, too, have the players go to pick up the clocks for the kindly professor, only to find a dockside gang trying to extort the clockmakers! The PCs deal with the initial squad of ruffians but later, a larger group comes back and kills the clockmakers. 

Then the PCs are asked to help safely transport a large amount of gunpowder, that part of the city is very rough. Afterwards, they meet the benefactor at the steps of the museum to get their rewards. 

The next week the dragon skull is on display and boom! Explosions! Theft! Murders!! The PCs are now framed by other evidence left at the scene. Their mysterious benefactors estate is now empty and a painting sits on an easel in the study, next to a discarded disguise kit. 

That’s how I like to play that scenario, give the villain a goal, small reasonable steps to get to it, and let the players help them, then instead of being rewarded, they get blamed for it. It never fails to work :)

good luck with your game!

Fun fact about Moriarty: He's only in one story and his rivalry with Sherlock is effectively retconned over all of the othe stories. Sherlock only briefly had a Moriarty, but he did kill him in the first story he appeared in.