Thanks and Do what you like. (Please don't finish the story) He can try to create Essences (a challenge for the MC), give them to companions who want to explore, choose someone from a story to change and mess up the plot if he wants, show why it happened, show how it could have been if it had been like this, Just be careful with those things that we know fans and readers of Fanfics hate. NTR, a disconnected story, random events without it being a Universe of Randomness.