After the War of Wrath in which the Valar of Valinor destroyed the forces of Morgoth and broke the sub-continent of Beleriand. In-lore, Sauron had a genuine change of heart and felt sorry for his actions, but strayed from his path and continued down the path that we know.

This takes place at that oft-ignored epiphany, but, instead of treading the path of darkness, he takes time to find himself. So he wanders the multiverse in search of something, what that something is, is anyone's guess. Just as luck would have it, he would arrive in a world that, while strange, would set him on the right path.

… But his travels haven't gone unnoticed.

(Rated Teen to be on the Safe side)