Had to scrap the main character and now I'm stuck...

I have been in your exact same shoes. First of all, I'm sorry! It doesn't feel good to invest that much effort in a character only to drop him/her. It sucks.

Fortunately you have good awareness and you're able to make these difficult decisions. Many people decide to trunk novels at this point because it's not worth salvaging. I can tell from the way you talk about it that you believe in your story.

I have done the tactic that you're suggesting. I've never done it with myself, but I have invented a few side characters and written side stories (within the world and plotline) to see if any characters/plots work out. Of course, these test scenes won't get published. They were really just for me. This trial-and-error method takes time and investment, but it might work for you.

Give it a go. Write yourself searching for a chosen one. I've done similar things. Remember, at the end of the day the only right method is the one that brings you solutions. I think your method is creative, and who knows? Maybe you'll find some extra side plots you weren't aware of. Maybe you'll find a bigger problem that needs to be solved in book II.

I agree with Blinkk here. I think it's a good idea that you came up with. I would definitely try it out. It might sound much better that way and you can get a clearer perspective on it.

If you have great world-building (which it sounds like you do, I can feel your excitement!) don't give up on it just because the mc didn't work. You have a lot of material to work with.

Since you're having trouble working your way through this thing working forward, consider going backward. Start from the end. It sounds like you know where you want to end up.

Abaddon is a villain, not merely an adversary, and it sounds like he's pretty evil. And someone will have to step forward to rid the world of him.

Okay. I don't know the tech/magic levels you're working with, but that's mostly a detail, as long as it's consistent with your world-building. It sounds like you want a hero to oppose him. And it also sounds like you want a hero that has to grow into it--no James Bond types.

Heroes usually grow into their roles for personal reasons. They don't start out wanting to save the world. They want to save their families, or bring major payback to the SOB who messed up their lives, or avenge the death of someone who shouldn't have died. There are some other possibilities, but those are the most common, and common in this area isn't necessarily a bad thing. It means you'll have a character a lot of people can relate to.

Your hero can move forward from their personal motivation with guns blazing, like in the original Die Hard. They can be a reluctant hero, even to the point of being an antihero. They can have varying levels of being flawed. It might be important to decide what kind of character you want in these dimensions.

Anyway, once you've figured that out, try to work back from there. If you get stuck working back, maybe try working forward again to see if you can get it to meet in the middle somewhere.

Everyone's a little different. I know I can't plot until I have my main cast. My plots flow from my characters. And my characters come from my themes. In the last story I finished, WWI was the antagonist, and I put all my loathing for that kind of conflict in my tale. I started with that, came up with a guy who could carry that fight (a reluctant hero--a farmer), and then I started plotting.

Don't know how your mind works, but it's a possible place to start.

Are there any characters that your first MC has interacted with during the story that you felt came alive in the interaction or telling? There are sometimes side characters that are more interesting and may have more room to move and grow than the MC.

What if the villain is actually the MC?