Let’s talk the basic mechanics of ruling the world - I apologize for the lack of specificity, but I have had it made clear to me that even the most innocuous use of historical example may be punished under forum rules.

First you would need a mechanism of governance. A method wherein the parties involved have delineated privileges and responsibilities. This obviously looks very different if Unity has said “that’s it, next war that breaks out I nuke both sides into genocidal oblivion - that’s my only rule” as opposed to a system where her she has effectively built an absolutist world-state. There is of course a wide range between them, which is going to delineate different procedures, rights, and responsibilities to each party.

Which brings us to the next point: are there supposed to be sub-entities beneath Unity with different degree of autonomy? What are they? What degree of internal administration and autonomy are they allowed? Do the constituencies they represent actually obey and listen? Arguably extracting some simple promises from the head of the elves who has already managed to establish dominance over all elven kind is going to look very different than imposing Juris Civilis Unity on twenty competing elven nation-fleets who don’t accept the idea of there being a “King of the Elves” to begin with.

Once you have those two worked out to a degree that can be “realistically” (for a world that is decidedly fantastic) enforced, then it becomes a matter of getting there.