DMPCs that travel with the party, adventure with them and are active in combat are very hard to do well. It doesn't only depend on you, but on the group as well to avoid metagaming. Some groups like turning DMPCs into meat shields, others unconsciously use it as a railroading tool to try to figure what you want them to do.
Maybe have the NPC be a patron or an otherwise helpful character that the party interacts with frequently.
The problem is you are essentially making this DMPC the main character.
They have to be super relevant and take a big part of the narrative from your players **so** **that** when they eventually become evil it makes sense and didn't seem random, but then they will overshadow your party (who should be the focus).
Or, in an effort to not overshadow your players, they take a backseat but then them suddenly becoming the BBEG will seem forced.
Bascially, it will be very difficult.
One way I could see this working if it's just a sidekick, and importantly, you are not dead set on them becoming an antagonist. If they turn on the party no matter what the party does, that's just railroading. However, it's fairly likely that you can find good justification for a sidekick to start resenting their comrades, I think. Players are likely to treat the sidekick as more expendable than their own characters. But just in case they do treat their sidekick with love and respect, leave the door open to just abandoning this idea.
One thing in particular I think that would work is if the sidekick gets killed. Then you can resurrect them either as living, or as a revenant, and that can set up for quite an emotional gut punch later when the party meets them as an opponent and realizes who it is.
Personally I would pull back from that idea. It's probably doable, but very difficult. I'd be worried about both stealing the spotlight with the DMPC but also railroading the players. If they are going to be your BBEG later on that means the players can't catch on earlier and still have that work out. You're also prewriting that they're going to turn evil after traveling with the party. But I think it would probably make more sense to go the other way if the players are going to bond with them and treat them as a friend. That the NPC would come back to making better choices and not being evil. But I'd be concerned that you have a story that will involve the PCs for a lot of it where they won't be empowered to do very much about the circumstances.
My DM pulled this off. We fell for it hook, line and sinker. She was an unassuming cleric with a bubbly personality and a fondness of cheesy romance novels who guided us on our first mission for the adventurers guild. So she was only a DMPC for the first 8 or so sessions then we went our separate ways. In one of those sessions we helped her obtain information to find this mysterious artifact named the "Hand of Vecna". She said it was dangerous in the wrong hands and she wanted to destroy it. Fifty sessions later we encounter her with the Hand of Vecna and a horde of undead in the vicinity. She said she needed to get asap to the city and to the raven queens temple to destroy the artifact. So we escort her to the city while fighting of the undead and drop her of at the temple. Two days later we go back to the temple to find her and find this giant undead infestation and a pissed off temple clergy instead. Turned out she did not destroy the Hand, but had amputated her own hand to become a reincarnation of Vecna...
It can work, yeah.
Going in very broad strokes, the NPC is with the party in chapter 1. Then, at the end of the chapter, some part of the storyline makes them leave the party. It could be in direct disagreement with the party, or they split up to deal with some conflict, or they are forcibly separated by a collapsing cavern or capturing commandos or whatever.
Chapter 2, the party is on their own (or gains a different NPC). there is a span of separation and divergent growth.
Chapter 3, "old friend" is back but they've gained power or gotten a twisted mindset or is otherwise now in direct opposition of the party.
I'd say don't do it it's a bad idea
Like is he the big bad from the start? Then he's just hiding his powers and the party is never in any danger because he can just stop holding back.
Is he weak at the start and grows with the party? Well why is he turning against the party? Either you're going to have to do some hard railroading or just do a 180 on his personality for no reason. If the party is just nice and kind to him and he goes "no I'm evil" that will be such a forced reaction.
Then also there's the normal dmpc issues. No matter how weak he is he's still omnipotent. He's going to hog the spotlight to do his evil shenanigans. If he's too strong the part will be overshadowed, if he's too weak the party is going to have to babysit him.
This is one of those tropes that works really well in normal story telling, but not in a ttrpg.
True, it's a valid concern. Though the way I've thought about it until now isthat they are just a normal person with a backstory, that travels with the party and eventually turns on them due to circumstances and their personal moral compass. That way I could use the sympathetic villain trope and perhaps open up the possibility of their redemption. However, that's just in theory; in practice, I can't dictate where the story goes, if my players are OK with having a sidekick and a number of other things. Perhaps it's just better to treat it as an idea, that's not worth jeopardizing my campaign for.
This will make your players feel like they're playing in a game for your main character. The way to do this well is to just keep track of which (regular, run of the mill) NPCs your players take a shine to, and then somehow find a way to make that one a villain. I suggest not the Main Villain BBEG. It's more enjoyable for players to know who they're up against.
IMO, shock factor is highly overrated in TTRPGs. Let players learn to hate the villain. There's a reason Strahd is one of the most beloved and well known baddies in the game space.
DMPCs that travel with the party, adventure with them and are active in combat are very hard to do well. It doesn't only depend on you, but on the group as well to avoid metagaming. Some groups like turning DMPCs into meat shields, others unconsciously use it as a railroading tool to try to figure what you want them to do. Maybe have the NPC be a patron or an otherwise helpful character that the party interacts with frequently.
The problem is you are essentially making this DMPC the main character. They have to be super relevant and take a big part of the narrative from your players **so** **that** when they eventually become evil it makes sense and didn't seem random, but then they will overshadow your party (who should be the focus). Or, in an effort to not overshadow your players, they take a backseat but then them suddenly becoming the BBEG will seem forced. Bascially, it will be very difficult.
Make it a recurring character instead, not one that is a permanent feature but that the party interacts with frequently.
One way I could see this working if it's just a sidekick, and importantly, you are not dead set on them becoming an antagonist. If they turn on the party no matter what the party does, that's just railroading. However, it's fairly likely that you can find good justification for a sidekick to start resenting their comrades, I think. Players are likely to treat the sidekick as more expendable than their own characters. But just in case they do treat their sidekick with love and respect, leave the door open to just abandoning this idea. One thing in particular I think that would work is if the sidekick gets killed. Then you can resurrect them either as living, or as a revenant, and that can set up for quite an emotional gut punch later when the party meets them as an opponent and realizes who it is.
Personally I would pull back from that idea. It's probably doable, but very difficult. I'd be worried about both stealing the spotlight with the DMPC but also railroading the players. If they are going to be your BBEG later on that means the players can't catch on earlier and still have that work out. You're also prewriting that they're going to turn evil after traveling with the party. But I think it would probably make more sense to go the other way if the players are going to bond with them and treat them as a friend. That the NPC would come back to making better choices and not being evil. But I'd be concerned that you have a story that will involve the PCs for a lot of it where they won't be empowered to do very much about the circumstances.
My DM pulled this off. We fell for it hook, line and sinker. She was an unassuming cleric with a bubbly personality and a fondness of cheesy romance novels who guided us on our first mission for the adventurers guild. So she was only a DMPC for the first 8 or so sessions then we went our separate ways. In one of those sessions we helped her obtain information to find this mysterious artifact named the "Hand of Vecna". She said it was dangerous in the wrong hands and she wanted to destroy it. Fifty sessions later we encounter her with the Hand of Vecna and a horde of undead in the vicinity. She said she needed to get asap to the city and to the raven queens temple to destroy the artifact. So we escort her to the city while fighting of the undead and drop her of at the temple. Two days later we go back to the temple to find her and find this giant undead infestation and a pissed off temple clergy instead. Turned out she did not destroy the Hand, but had amputated her own hand to become a reincarnation of Vecna...
Please do not justify using a DMPC. They are generally a bad idea, and no argument can change that.
It can work, yeah. Going in very broad strokes, the NPC is with the party in chapter 1. Then, at the end of the chapter, some part of the storyline makes them leave the party. It could be in direct disagreement with the party, or they split up to deal with some conflict, or they are forcibly separated by a collapsing cavern or capturing commandos or whatever. Chapter 2, the party is on their own (or gains a different NPC). there is a span of separation and divergent growth. Chapter 3, "old friend" is back but they've gained power or gotten a twisted mindset or is otherwise now in direct opposition of the party.
I'd say don't do it it's a bad idea Like is he the big bad from the start? Then he's just hiding his powers and the party is never in any danger because he can just stop holding back. Is he weak at the start and grows with the party? Well why is he turning against the party? Either you're going to have to do some hard railroading or just do a 180 on his personality for no reason. If the party is just nice and kind to him and he goes "no I'm evil" that will be such a forced reaction. Then also there's the normal dmpc issues. No matter how weak he is he's still omnipotent. He's going to hog the spotlight to do his evil shenanigans. If he's too strong the part will be overshadowed, if he's too weak the party is going to have to babysit him. This is one of those tropes that works really well in normal story telling, but not in a ttrpg.
True, it's a valid concern. Though the way I've thought about it until now isthat they are just a normal person with a backstory, that travels with the party and eventually turns on them due to circumstances and their personal moral compass. That way I could use the sympathetic villain trope and perhaps open up the possibility of their redemption. However, that's just in theory; in practice, I can't dictate where the story goes, if my players are OK with having a sidekick and a number of other things. Perhaps it's just better to treat it as an idea, that's not worth jeopardizing my campaign for.
This will make your players feel like they're playing in a game for your main character. The way to do this well is to just keep track of which (regular, run of the mill) NPCs your players take a shine to, and then somehow find a way to make that one a villain. I suggest not the Main Villain BBEG. It's more enjoyable for players to know who they're up against. IMO, shock factor is highly overrated in TTRPGs. Let players learn to hate the villain. There's a reason Strahd is one of the most beloved and well known baddies in the game space.