Yes! Exactly. I want to go with this approach but I want to find a way for it to make sense, if this being is so powerful. How come this gruoup of protagonists is able to eventually defeat it in the end. Still trying to work on that one.
The issue is with the two variables, power and timer. One way to solve it is to take one of them and tone it down. Maybe he didn't arrive a very long time ago but only recently? Maybe he arrived a long time ago but did not have any plans to do any harm until a short while ago? Or maybe he isn't that powerful?
The thing with power is that it's relative. How powerful a character seems is determined by the point of view of your protagonist. Twelve year old Billy the Bully isn't gonna make you sweat. If he threatens you someone will have to scrape his ass of the wall. But to 8 year old Tom he's going to be this old, near adult who's a lot more experienced and bigger.
The second thing with portraying a character as powerful is that it's less about how much power you ascribe to him but what he accomplishes. You can call someone an undefeatable god the entire story and the player will never really feel that it's true, because you're merely telling him. You need to show the player how the actions of the antagonist affect him and the story. All some antagonists need is clever words to turn friends into enemies and cause kingdoms to fall. They're not physically powerful or omnipotent, but they use what they can do with such skill that the effects of it ripple outward through the world.
Take an antagonist who's clever with words and very convincing. Someone whose mind is like a serpent, always circeling around the player, looking for something to hook his teeth into. Who actually makes the player question who is right and who is wrong, and whether opposing the antagonist is actually the right thing to do. Someone who is charismatic and compelling, who can get people to look at things from his perspective. And now imagine that near the great finale, that antagonist is willing to sit down to discuss a path that won't result in a war between two factions.
In any other story, that would be promising - except you know that he's incredibly good in convincing people to see things his way. And then, just before the last round of discussions, the antagonists asks the player for leave to discuss something with one of his companions. Can you imagine what the player is going to feel like, knowing that one of his companions is right now in one room with the one person who can convince anyone?
So you don't need someone who is the most powerful thing in the universe and can corrupt anything, necessarily, to have a powerful and frightening antagonist.
The other route would be to make an excuse. This is often the traditional way people in sci-fi and fantasy approach it. Yes he IS incredibly powerful, but he got hurt and for a couple millenia had to recover his powers. Stuff like that. It can kinda work, depending on the execution, but it's always a bit cheesy by nature and you need to cover that up with convincing storytelling. It's best not to spend too much time on the excuses, though, because that draws attention to them.
Two other points: Be careful with the idea that the villian is responsible for all bad things in the world. That's usually a way to saddle all responsibility on him to make his removal really necessary but it's often not all that believeable. There's never really one evil. It's usually a lot of things coming together that lead to catastrophes, mostly selfishness or ignorance of the consequences of one's actions. The danger the antagonist represents and the necessity of his removal is determined by the perspective you create and your storytelling.
You can write a story about a young man who intends to kill the greatest hero of all time, a guy loved by all who saves princesses and slays dragons, because he killed his sister who worked as bouncer for a criminal establishment to get enough food for herself and her brother on the table. It doesn't matter that there's an evil wizard out there who's threatening the world and that the hero is greatly needed. If you write a compelling story about the love the sister had for her brother and the things she did to allow him to survive in a dark and uncaring world, the one moment of casually dispatching his sister because she's in the way is enough for the player to justify the death of the hero.
The second is: try to get a very clear perspective on what the antagonist tries to accomplish and the methods he uses. What's the purpose of a terrorist doomsday organization? What is he trying to accomplish with it?
Because a terrorist organization is an organization that attempts to achieve a goal, often politically, through spreading terror. The idea is to incite fear in people's minds that will affect the decisions they make. They don't kill people because they like killing people but because they believe the fear and horror resulting from it will ensure that their opponents make decisions that will be beneficial to them.
If he can corrupt people, why the need for fear? Does he draw some kind of supernatural power from fear? Is his ability to corrupt people limited to those who fear him?
Or maybe his terrorist organization is only for show- something the world can rally against, except his own corrupt humans have been put into high positions where they are going to take control of the resistance that's forming, giving him and his corrupt people unprecedented power by using the justification of combating the terrorists.
The import thing is that the decisions he makes and the methods he uses align.
There's this danger that sometimes you run away with an idea that you fancy and that you'd like to see happening - but you don't really have it connected to the story. Happens to everyone. The key is to either link it to the story or scrap it.
You often see bad anime where they don't understand that. They end up with organizations of justice or evil that don't really make sense and, in the way they're organized, could never even accomplish any of the things they supposedly intend to do. They're paper tigers who only exist because there's a need for an antagonist, but they don't really link into the story or the world.
Each protagonist has their own demons to face. And I wanted to draw a connection between the events transpiring them and how the characters deal with such events according to how they develop and experience the journey.
Are the protagonists travelling together and experiencing the story together or are you aiming for seperate narratives with each of the protagonists having their own story arc that's locally independent of the others but linked in the greater content? (e.g. are you switching through characters throughout the story?)
