Final Fantasy 10
In Final Fantasy 10, a war is taking place between Zanarkand (led by Yu Yevon) and Bevelle. Zanarkhand found some pretty creative ways to fight this war. They sacrificed humans who would become Fayth that subsequently dreamed up weapons for the Summoners of Zanarkhand to use. Those are the Aeons. This isn’t to say that Tidus is an Aeon. It gets a whole lot more complicated than that.
See, Yu Yevon had an even better plan to win against Bevelle – have Zanarkand exist as a dream by the collective Fayth and then have it summoned somewhere else as a separate city in Spira. This would ensure their continued existence and Sin was created to act as a protector for the dream city.
However, since it’s composed of the spirit of Jecht, Tidus’s father, it actually attacks the city to push Tidus to end this whole farce (or “cycle” whatever you want to go with). So in the end, when Tidus disappears, it’s because the fayth have finally stopped dreaming and the denizens of the dream city fade away.
Of course, he reappears in Final Fantasy 10-2 but that’s another mess altogether. For the time being, take solace in the fact that Tidus may have been some elaborate dream but he eventually does have his own existence, thus leading to his reunion with Yuna. And then they lived happily ever after, doing awkward laughs into the distance.
