Harold Porter and the OP-NPC

That's a really tough one. I don't think it's doomed to be a trainwreck. It could be a good game.

That said, Morrowind was a way more compelling story than Oblivion.

I don't know if you're familiar with the games, but just in case, here's a brief summary. In Morrowind, you find out that you're the reincarnation (well, actually one of many reincarnations) of a great hero who is destined to overcome the BBEG who was essentially created during your original life. In Oblivion, you have to find the lost son of the emperor and help him become the hero who can overcome the BBEG and "shut fast the gates of Oblivion." They were both great games. But I'd go to the mat saying that Morrowind was a better story. And a huge part of that was the feeling I got while playing it of being a truly important part of the world.

It feels petty, but "go explore this ancient abandoned ruin to find a powerful artifact that you once owned in your past life" was a hugely different emotional experience than "go explore this ancient abandoned ruin to find a powerful artifact that you can give to Martin so he can do cool stuff with it." In one I felt like the hero, and in the other I felt like a glorified errand boy. Oblivion told a good story, but in the end it wasn't MY story. I just got to play a role in it.

And I think that's the risk we take whenever we make a story center on an NPC. Even if the players have real choices to make in determining whether this savior NPC rises to his destiny or not, they may in the end feel like they're the sidekicks instead of the heroes. And crippling the character's physical stats may actually make that problem worse rather than better. The most annoying thing about the character of Martin in Oblivion was that he spent most of the game sitting on his butt and keeping out of danger while I did the dirty work. That didn't make me feel more like the hero, it made me feel even more like an errand boy. You don't want your players to feel like they've been strapped with a liability they have to take care of.

All of that said, Oblivion wasn't the best possible execution of the "helping an NPC rise to greatness" storyline. I bet you could do a way better job. And I can think of a few ideas which might help sidestep the pitfalls.

First, the PCs have to know the NPC and, more importantly, learn to LIKE the NPC long before they begin helping him or her. It has to almost feel like it's their idea to help, rather than the story being forced upon them. Let the NPC come in and out of the borders of the story at the beginning. Catch their interest. Intrigue them in who this person is and their story before any opportunity to join their quest presents itself. Because this person will BE your story, in a very real sense. He or she must be captivating.

Second, make the character strong. Not in mechanical terms, though there's a case to be made for that too. But make them a truly strong character, with a strong will and firmly held beliefs. The more the character feels like an apprentice that the players are helping along to greatness, the more resentful they may become that all the work they are doing is for the benefit of this "dead weight with a destiny." 

This leads to a third point, which may catch me some flak. Consider making the NPC female. A female character can more easily be strong, competent, and capable without coming across as a boss or a taskmaster. If you play it well you may even successfully tap into "damsel in distress" emotions, even if the NPC actually defies such stereotypes. Think of Princess Leia in the original Star Wars. She's anything but a damsel in distress, and she actually takes instant charge of the situation, and yet it doesn't feel as though she takes away from the agency of Han or Luke. And they argue back (Han particularly). Try to imagine a similar situation in which they had broken out a highly ranking male Republic officer who began barking orders at them. The emotional tone of that interaction would be drastically different, simply because the "commands" of Princess Leia are perceived by both characters and (I suggest) the audience to carry less weight than would those of a man of equal rank. Is this perception due to latent sexism? Probably. But if you can use latent sexism to tell a compelling story, while simultaneously challenging the same sexist ideas? I say go for it.

I'm going to call this wall of text quits before it becomes a blog post. Hopefully some of it is helpful to you. Whatever you decide, best of luck!

I have to disagree with this one. Emotional investment in the NPC is critical in this type of story, and it seems to me that a preexisting "backstory" relationship is actually a lot harder to get emotionally invested in than a character you learn to love over time.

If I'm told "this is your kid/this is your little brother/this is your student you love," I'll have a really hard time role playing that relationship convincingly largely because my character supposedly knows and loves this character, but I as a player don't yet. A really good role player can probably put themselves in the right mindset to emotionally invest immediately, but I suspect that such excellent role players are few and far between. I'm certainly not one. And I'd suspect, perhaps cynically, that what's really going on in that good role player is superior acting skills, rather than true emotional investment in the character.

I think real emotional investment in fictional relationships requires, for most players, that player knowledge and character knowledge develop side by side. As your character gets to know and love the NPC, so do you. Stomp, for example, was a truly beloved character because of the stories that grew out of his interactions with the PCs. I would bet money that Chris and Mitch have never had a backstory relationship (parents, children, siblings, etc.) who was as memorable as Stomp the Goblin King.

None of that is to say that backstory relationships CAN'T develop effectively into real emotional investment, but I think it's genuinely harder, especially in the critical first few sessions of play.

Hey you two. Wow! thanks for the plethora of advice and ideas.

I'm at the end of my shift so this'll be a little short reply for now:

I'd already planned on having the titular npc be the daughter of the party's benefactor, a noble who first sent them off towards Phandalin.

I agree that people tend to get more emotionaly involved with female characters, especialy children. I had a whole term paper about it back in college going on about the taboo of a woman being hurt, and the protective instincts of adults and whatnot. Brief example: A whole platoon of male soldiers is wiped out and the audience sees it as commonplace cannon fodder. A young girl is crying in the middle of the war zone and our attention and emotions are immediatly brought to the forefront.
I theorize that it's not overt sexism, but something that's socially ingrained. It can be changed over time, but not pried from our systems.

That aside, you made a good point of introducing the character to the players sooner rather than at the beginning of a new campaign. This way they get to know her sooner and already have an idea of the character. I know just the place to bring them in as it will also help show case a part of her personality that may make her endering or, at the least, an intreguing curiosity.

Okay, I'm beat, more talks tomorrow.

Good point. There's several oppurtunities here with the ranger's dead family (one could have escaped the slaughter), a grieving husband that the half-elf rogue befriended, and even a priestess of Tymora that both the bard and the paladin are trying to romance.