So.... question.

What are peoples general opinion on invincible NPCs or rather unwinnable situation? The basic idea is that i want to introduce an enemy group into the game, that are meant to be a reoccurring part of the game. as part of the narrative, the group isn't meant to be able to defeat them yet and encounter them later under different circumstances. I guess they aren't really invincible per se, but just really really really op. a group of several level 9 or so enemies against my current group of 4th level players.

I generally get the idea people don't like facing unwinnable scenarios, but I think it would enhance the narrative quiet a bit and would also introduce previous lacking stakes into the world, but I'm still fairly inexperienced in this kinds of things, so i figured I ask you. What is your opinion on it? 

to quote obi wan kenobi: "You can’t win, but there are alternatives to fighting".

Remind players that they don't have to fight, let alone kill, everything. You could have the party go into a town that gets attacked by the enemy group but have alittle "cinematic" that tells of a mage like character throwing high level spells (fireballs, cone of cold etc), fighter types striking multiple times a round, Sneaky types appearing and disappearing or skipping from roof top to roof top. Then have the players have to stealth their way around the combats to escape and eventually get hired to find the enemy group, investigate or infiltrate them and finally take them out.

Quote from Paefny >>

 

I generally get the idea people don't like facing unwinnable scenarios, but I think it would enhance the narrative quiet a bit and would also introduce previous lacking stakes into the world, but I'm still fairly inexperienced in this kinds of things, so i figured I ask you. What is your opinion on it? 

Nearly impossible to pull off in a way that will not frustrate your players.  Players hate to lose. No matter how mature, how experienced, how dedicated to the pure craft of RP, they hate to lose. They will not like facing unwinnable odds. They will feel it is unfair. They will think you are "trying to beat them" as a DM. No amount of being reasonable or explanatory will solve this. They will hate it. Period.

If you do this, you will have a very angry group of players who will almost certainly become petulant and disagreeable during the latter parts of the encounter, as it becomes clear this was a no-win scenario and manifestly (and deliberately, because you have set it up) unfair. You might even face people telling you they don't want to play anymore. Telling them "I am just setting up an archvillain for you to fight later" will not solve it for some people.

I've seen this done successfully once. By none other than Matt Colville in his first Chain of Acheron episode. In that episode, he killed off his best friend Lars' character, the leader of the Chain, and destroyed half the rest of their NPC retainers, and they had to flee the city on a boat. This did not actually anger his players, but only because they knew it was going to happen ahead of time. He gave them a choice of 4 campaigns and they picked the Chain idea -- being the commanding officers of what used to be a large mercenary army that was down to a couple dozen, and they have to build it up. Then he asked if they would like to play out the "fall of the Chain" or just use it as a backstory and they said, "Let's play it out." Then he said, "Someone's going to have to die," and Lars and another good friend of Matt's, Phil, said, "You can kill one of us." So they went into the first session knowing this was going to happen. That can work. And it did what you want to do -- it set up an archvillain for the rest of the campaign. But the players actually asked to play through their own defeat, which is the only reason Colville did it.

And note: although the players were OK with it, Colville later said that half the people watching the stream were having a fit, typing IN ALL CAPS into the discord that Matt was being an unfair killer DM, that Lars had been ill-used, and so forth. It got so bad Lars had to go onto the reddit the next day to calm everyone down and say "Look, guys, I knew my character was going to die. I had a back-up ready on purpose. It's fine." But the fans were mad. My point here is, they weren't even playing and many people still took umbrage at the setup.

I highly recommend you find another way to make these guys arch enemies without having an in-combat defeat of your party.

A couple of thoughts:

• Unless you're railroading your Players, you have no idea what the Narrative is going to be. Therefore you can't tell what will "enhance the Narrative [quite] a bit". Set up the initial situation, set up the central conflict, design good NPCs and Factions. That's your part. Your Players' choices and actions are their part. The Narrative occurs where those interact. You don't have control over the Narrative; don't try to force it.
• Literally unkillable NPCs are railroading your Players, because the DM is going to protect those NPCs until such time as the DM had pre-determined it is dramatically appropriate for them to be killed in a scene they've pre-imagined. It's called "plot armor".
• Practically unkillable NPCs are very problematic, and need to be handled very carefully. Your Players are likely there to play heroes, and heroes don't run away or surrender. Plus in the current RPG culture, a lot of Players are going to assume that if an encounter exists, then the DM is going to have made sure it's balanced, and that the Players can win it. Presenting encounters which there is no hope that the Party can win runs the very real possibility that the Party will charge on in anyways, and TPK themselves.

Now, if what you want to do is establish a villian, or an antagonist faction, without having the Party take out the main Adventure antagonists, you still can do that without railroading. A few options:

1. Don't present unkillable NPCs to the Party. Present them with completely killable minions, which act in such a matter as to establish the villainy of the organization to the Party,  and what kind of people they're up against, yet can be defeated by the Party. There's two flavors here: a) the Party doesn't encounter the evil faction's leadership, they just encountered lieutenants or lackeys, and the faction's true leadership is now aware of, and angry at, the Party, b) the Party does manage to take out the faction's actual leadership, and someone even worse moves into the power vacuum.
2. Don't present them with an encounter at all. Present them with the aftermath of someone else's encounter: a burned out village where the actions and character of the bad guys can be firmly established to the Players, and important information and clues can be conveyed to the Party via the stories of the few remaining survivors. This can even be used to convey to the Party the level of power they're need to be at to take on the main/new bad guys, because they'll have some idea of the strength of the main antagonists now.

Foreshadowing, and setting up the stakes in the Adventure is a legitimate - even essential - tool in the DM's toolkit. Your motivation is sound.

Just try to make sure that you do it in a way that doesn't trivialize your Players' agency. Let their choices, and their actions change the Narrative. 

Don't present unkillable NPCs to the Party. Present them with completely killable minions, which act in such a matter as to establish the villainy of the organization to the Party,  and what kind of people they're up against, yet can be defeated by the Party. 

This is the Lord of the Rings model. They never encounter Sauron. In fact in the books you never even see him. Yet you know the whole time he is the unkillable arch-enemy.

Yet his minions, the orcs, are eminently killable.

A thought provoking question. The answers thus far have been an interesting read.

You are spot on. Players do not like unwinnable scenarios. I've learned this the hard way myself. It may feel like a good idea to present an "unwinnable" scenario for XYZ reason. To set the tone of the campaign, to introduce a BBEG they need to love to hate, or to show a cinematic moment of destruction/despair. 

I'd start by asking yourself: "What does this unwinnable encounter add to the game?" and follow that question up with "What makes it unwinnable?" and finally ask "...Why?" Weigh those reasons against the importance of the player's fun factor.

What makes the NPC unbeatable and why? Are they legitimately immune to death or are they just very high CR compared to the party? I think it is fine to present your party with enemies that are too difficult for them to defeat at the moment. But the encounter those OP enemies exist within shouldn't be centered around trying to defeat those OP enemies. Those enemies should only be used to heighten the stakes and strike fear into the party as they face a more manageable encounter they can win. 

For example, I'm playing in a campaign where our party accidentally brought enemy forces upon our homebase town. We couldn't hope to defeat those enemies ourselves and many of them were much stronger than us. Our focus was on protecting the town from smaller raiding parties, saving named NPCs we had grown to know throughout the campaign, and protecting an NPC from being kidnapped. Had our goal been to take down the commander it would have been impossible. Instead, the scenario was framed around what we could do while all of these "unbeatable" baddies narratively clashed with good NPCs that could stand against them. 

The important takeaway from this example is that the party existed within a hopeless or dire scenario, but the encounters we interacted with were not unwinnable. This concept can be applied to whatever unbeatable or unwinnable situation you have in mind. 

If a scenario is unwinnable or an enemy is unbeatable, then there's really no point for the party to participate. It becomes a cutscene or a vaguely interactive story. So there needs to be something the party can do in this scenario. Something they can succeed at, even if there is still a decent chance of failure there.

If you want to enhance the narrative by introducing a currently unbeatable BBEG, introduce them behind the scenes. They can appear in dreams, they can send messengers, they can appear as illusions before the party. They can destroy a party member's home town, or threaten to hurt the party member's family. Everywhere the party goes there can be signs the BBEG and their army have done horrible things that the party couldn't have hoped to stop. And while the party may not be able to beat the top commander in an outright fight, they might still be able to stop that enemy from doing the bad thing they're about to do. A well placed spell, a clever use of tools, or a praise to the gods above a high Religion check.

For reasons as Biowizard stated. Try to avoid such clear unwinnable situations. However... you can make it an unwinnable fight in which the bad guys get away. Just give something else to the players. Make it so they still "win" a piece of new information to move forward with. That way players can find it more acceptable since it isn't a loss of time. They still gained something useful and meaningful out of it.

Also nothign says that this NPC is very important and powerful... is by having many tiers/managers that your party has to go through in order to reach the villain.

You can set it up so that the players themselves fight a very winnable fight, but see it as part of a larger unwinnable one.

For example, Big Bad Evil Guy appears, and sends a wave of minions at a town of civilians while he, I don't know, gets a sacred relic from the town church or something. The PCs get a task - protect the civilians as they get away from the minions across a the bridge. The PCs fight a very winnable "fighting retreat" where they retreat across the river then torch the bridge, with their "score" being how many civilians they save. The PCs can, if successful, save ALL the NPCs, leave them room for this stunning victory!

...but note that this "stunning victory" also shows them just how far they were from actually defeating the BBEG, since it took all their resources just to fight his minions to a draw.

Quote from ftl >>

You can set it up so that the players themselves fight a very winnable fight, but see it as part of a larger unwinnable one.

For example, Big Bad Evil Guy appears, and sends a wave of minions at a town of civilians while he, I don't know, gets a sacred relic from the town church or something. The PCs get a task - protect the civilians as they get away from the minions across a the bridge. The PCs fight a very winnable "fighting retreat" where they retreat across the river then torch the bridge, with their "score" being how many civilians they save. The PCs can, if successful, save ALL the NPCs, leave them room for this stunning victory!

...but note that this "stunning victory" also shows them just how far they were from actually defeating the BBEG, since it took all their resources just to fight his minions to a draw.

This is a brilliant suggestion. I'm definitely jotting this one down in my "DM book of tricks".

Wait... you have the DM's Book of Tricks? How did you get your hands on a Legendary Artifact?

How many GP do you want for it?

Quote from BioWizard >>

Wait... you have the DM's Book of Tricks? How did you get your hands on a Legendary Artifact?

How many GP do you want for it?

It's self-authored :) 

And I highly doubt there's anything in my collected notes which you don't already know :)

Solution is simple.   To quote the great Monty Python:

RUN AWAY!

It is very difficult to kill someone that runs away before the battle gets very far.   Give them enough hitpoints and other stuff to easily last 5 rounds and have them all escape on the 3rd round.

Best done with them laughing and holding up the McGuffin they stole from the players.   Ideally saying something like "I look forward to you retrieving other items for us. Hahahaha..."

I’ll add that not only is it annoying for the players, but also, they likely won’t do what you want. Players hate retreating from encounters, and they may not. This edition seems to have built in the expectation that DMs will only give fights balanced for the party under the current circumstances, so they will assume they can win. So if you are expecting them to realize they’re in a losing fight and retreat, they probably won’t, and you’ve got a tpk. They’ll look around for the win button on the nearby pillar, but they won’t actually run away. 

Recurring villains are great, but they are better when you build the suspense. Make them a boogeyman no one has actually seen. Then they run into an underling, then a lieutenant. Eventually they get wind of the actual bad guys. I don’t know if you ever saw the first season of daredevil on Netflix, but you don’t even hear the bad guy’s name until the third, of 10, episodes. Mystery and suspense are the key to every story. 

Also, as vedexent was saying, it’s really hard to force a recurring villain without railroading. The players need to be invested in defeating them, and that’s the sort of thing that usually happens best organically. That random orc who got away one time, the cleric who used word of recall to escape when she was at 5 hp.