However, before he makes his way to the empire's capital, he's abducted by a rebel group. This rebel group gives him a rundown of why the empire is looking for him: that he's the subject of a prophecy which is the very foundation of that empire and its eventual downfall.

It turns out, the empire is acting to fulfill the prophecy that will put the end to their empire, and willingly so. According to the prophecy, our protagonist will put the end to the empire, and all sentient life in the world, through a process of "ascension" (imagine an isekai version of the human instrumentality project, I suppose, but with way less magitek and more hand-waving). This rebel group wants none of that, however, and presents their case to our protagonist.

When asked about it, the rebels reveal that neither the empire nor the rebels know how this "ascension process" will occur, but both have faith that this is fated to occur, and that the protagonist appearing is a sign of that. The protagonist wants some time to think about it, and more importantly, some time to just take in all the events thus far. The rebels understand, and give the protagonist some time.

The empire, however, has discovered that the protagonist is in the rebel base, and had attacked. In order to spare the rebels from being destroyed, the protagonist escaped from the rebels (he's still technically their prisoner), and went along with the empire's troops.

Our protagonist was presented to the emperor, not as a prisoner, but as a guest of honor. Talking to our protagonist in private, the emperor presented the empire's case: they're acting on the prophecy, not because they're bound to it, but because they want to. The emperor also told our protagonist the truth of his existence in this world: he is this world's creator, literally their God. Everything that happens in this world is because he willed it to happen. This is his power all along: whatever he imagined, the world manifests.

Well, this is a shock to our protagonist, who asked for some time to think about the implications of everything he's found out so far. For all his powers as god of this world, however, our protagonist can't will it that he knows why he's the god of this world. This god, our protagonist, has no power over himself in this world.

The rebel group, after having been scattered after their base is dismantled, launched a desperate attempt to secure our protagonist. They were rendered helpless facing the empire's elites, but our protagonist asked the emperor to give them an audience (with the emperor) as well.

In this meeting, the representatives of the empire on one side, headed by the emperor himself; the representatives of the rebels on the other, gave their arguments to our protagonist at first, which devolved to a shouting match between the two sides. Our protagonist started dissociating, and found himself lying inside a tent, in the middle of a forested mountain, in what is presumably the real world.

This real-life version of our protagonist is not feeling very well, however. He can barely open his eyes. He's incredibly tired, and more importantly, suffocating to death.

That's the twist, unfortunately. This "isekai world"‌is his dying dream. This is why I think this is just my self-indulgence. It's a very formulaic "dark twist" on a cliché.