How can I fit a protagonist and his character arc to an existing world and plot?

Question

I began my project with world-building. Afterward, I decided on the overarching plot, and now I'm trying to populate it with characters, starting with my protagonist. I've figured out his core driving force, but I have trouble coming up with a growth arc for him.

Plot & Premise

My world is a classic fantasy mixed with cosmic horror. The evil wizard messes with forces beyond his comprehension, leading to his undoing before he can rise to power, so the protagonist gets to grow up in a peaceful world. (Think Harry Potter if Tom Riddle got himself killed before he could become Lord Voldemort.)

But because the two are connected by fate, whatever happened to the wizard has left a stain on the hero's soul, too. I haven't worked out the details—it may be that something's wrong with his magic, or he wades through life discontent, feeling like he's missing some fundamental piece of himself—but it's going to be the force that drives him down the same road as the wizard, in search for answers.

The turning point will be him accidentally unleashing what has become of the wizard upon the world. (Rather than a person, the wizard will have taken an intangible form and will spread like a virus. It can only be tracked through its effects on people, like in Bird Box.) He has to fix his mistake and defeat the horror before it destroys everything.

Problem

I'm struggling to come up with a character arc for the protagonist. The standard method is to give him some kind of flaw which he eventually overcomes in the climax. Alternatively, as described here, a past experience will have given rise to a harmful belief, which the character plasters over with another belief, and he must realize he's lying to himself and muster the courage to move past it; or something like that.

I don't know how to fit my character into that framework. His problems stem from an external source. No amount of internal growth will fix that. Do I need to give him another problem, one which, upon confronting and overcoming, will allow him to fix the external problem?

I should note that the cosmic horror is intended as a background element to enrich the world, like Tolkien did with his distant mountains. It is the theme of the story—fear of the unknown—and I built the world and the magic system around it, but the main conflict is in ethnic tensions (which spring from the same fear). My other great woe is trying to weave the two conflicts, the hero's exploration of the eldritch corners of the magical world and his position in the middle of said tensions, into a cohesive plot.

Answer 1

Don't try to write your story to satisfy the demands of some how-to-write book! That's stifling your creativity.

Put everything away, put a pencil and notebook in your pocket, and take a walk. Let your mind roam freely and write down everything, without censoring, what you come up with. Do this until you have an idea.

These questions might guide you:

• Who is your character when the story starts (before the inciting incident)? Where does he live, who does he live with, what are his goals in life, what does he wish for, etc.?
• What does your type of inciting incident do to someone like that? Is the quest a weight on the character's soul? Is he traumatized by the loss of his home, family, and friends? Or does it provide the freedom and adventure he has been hoping for all his boring, constricted life?
• What skills will he need to acquire to survive or fulfill his quest? Those can include emotional "skills" (e.g. the ability to kill an enemy).
• What will learning these skills do to someone like him under those circumstances?

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After you found answers to all these questions, and if you feel that you want to further refine your character arc, then use the books you have to help you polish it. But even then, don't let someone else's concept water down or destroy your own! Use their ideas to reflect on your story and decide if you want to change it or not. The danger is that if you blindly follow some formula that your story becomes generic and bland.

Answer 2

Reading over your summary, you appear to already have the seeds of one of two potential character flaws for you character to overcome.

Too Curious - Not Able to Let Sleeping Dogs Lie

The evil wizard got himself eliminated from the world by messing with forces he should have left alone? The only reason there's a problem is that the character couldn't leave well enough alone and he had to scratch the itch that an unfulfilled fate gave him? That's a pretty strong character arc / flaw, fitting nicely with cosmic horror: learning when not to look under the rock and see what pallid things squirm there.

This might mesh with a search for more eldritch knowledge, to put down the problem he first unleashed pursuing his connection to the wizard, only to eventually realize such a quest will only pile on more problems than before.

Learning to Choose For Youself - Overcoming Fate

A slightly different flavor for such a story might be about the character recognizing how has let himself be a pawn of Fate. He could grow by recognizing his "true self," apart from his fated (and corrupted) link to the villain.

Or, alternately, he could realize that he can actually choose for himself who he is, not in the sense of being true to some abstract "true self," but in deciding what he ought to be and working for what is really best. (Or can he? Dun dun DUN!!)

Answer 3

Reading your description, the problem for your protagonist seems clear to me:

He is not "himself". He doesn't understand himself, or why he is the way he is.

whatever happened to the wizard has left a stain on the hero's soul.

he wades through life discontent, feeling like he's missing some fundamental piece of himself.

This is the flaw. He is discontent, and doesn't know why. His soul is stained, he doesn't know why. He is missing some fundamental piece of himself, and he doesn't know why.

The hero's journey in this is one of self-discovery and self-realization. To understand how the magic in this world works. To understand where he fits in, because he doesn't fit in anywhere. You need to give him some failures, he will never fit into his society while he is missing pieces.

These failures drive him out of his current village or city, in search of a person, or place, or profession that will make him feel whole. He doesn't know what; he just knows, from his final failure in Act I, that it isn't here.

He then discovers magic-users, and becomes convinced magic will clear his soul, and will make him feel whole and at peace with himself. But he screws up the magic, and unleashes the evil wizard.

Battles ensue, the rest of Act II, and it doesn't look good for the hero. He is getting his ass kicked, again and again.

But In the beginning of Act III, defeated, he still won't give up. He finds one last book or magician. They tell him the most powerful magic of all -- he can bet his eternal soul. If he loses, he dies and his soul is destroyed. If he wins, the evil wizard's soul is finally and utterly destroyed, and the stains on his own soul will vanish.

He determines to do it, he would rather die than fail, and he succeeds. The wizard is destroyed, the protagonist is cured, his soul is spotless. And then, the end of Act III, he begins life in the "New Normal", a new man, with magical skills. What that means is up to you.

The journey here is self-discovery, and self-repair. It doesn't have to be any more complicated than that. He knows something is wrong, and whatever it is, it is ruining his life and happiness. That is the problem we open the story with, our hapless hero trying and failing, and failing, and failing. And the solution is what we close with.