Okay, so It's not the most original idea, but there's this guy who's a writer, he wanders and gets lost and comes to a strange room he finds himself lost in with nothing around. he finds that in this room he has the ability to control worlds, to take some from one world and put them in another, to move them in the world, bless them with power, the machine basically makes him a god of the multi-verse minus immortality or the power being his own. He thinks that if he can use the room correctly, he can make the ultimate story for his writings. I don't know what to do with the idea though
When he was at school, he studied English literature, and in his group there was always this enemy he had - his rival. They would compete to write better stories, the most gruesome and riveting. Your writer had a narrow defeat at the end of the year based on scores. Now, he's writing. He gets into this place, and all of a sudden the worlds he create all start to become ruined and damaged. He soon realises that there is another force, who is creating worlds of his own, while simultaneously worsening those of your protagonist. It turns out to be his enemy from school, trying to defeat him one last time. There you have an antagonist. Come to think of it, if you want the protagonist to succeed, you could say that the protagonist decides to use his rival as the basis of the antagonist for his writings . Hope I'm not too late.
I like all these if you're trying to have an action type story. If you'd gather go more G rated; give the man with words the chance to start seeing all of his worlds that he creates. Have him create a few and travel through them, enjoying the high at first, but slowly start to notice the flaws. The colorlessness will attack his senses, the lack of depth will make his worlds seem trivial. He can then make a new book; a book that has life.
If you write this as experiments in artificial intelligence in a virtual world, the story would be extremely plausible. You could have the simulated people initially wandering about their world carefree and aimless. The MC thinks that's boring. He chooses to stir them up by making some of them paranoid, some greedy, others affectionate etc. This setting, and the events that unfold, would lead the reader to the moral of the story, the theme, the message of significance that the author wants to covey to the reader, which is . . .
Hmm, it's a very intriguing idea for a story. Let's see... So your MC finds this room, starts using this room and the power within it to control and manipulate the multiple universes. At first things are going great, he's playing around with the worlds and has his fun with them but eventually his careless and irresponsible use of the power of the room results in several catastrophes in each world - wars, massive earthquakes and other kinds of disasters - his attempts to undo these only makes things worse. While he's struggling with all these, an ancient and malevolent force - could be some sort of deity or something just as powerful - becomes aware of him through his excessive use of the room's power and decides to find him and take control of his mind and body so it can control the worlds through him. Now Your MC not only has to deal with the disasters and the death and destruction he has inadvertently caused in the multiple worlds, he's also forced to fight this ancient force to keep it from enslaving him. You could have the evil force partially possess the MC to make his struggles more interesting. Anyway that's my take on your idea, hope you like it