Could you be a bit more specific on what sort of tone you want for the setting? The details seem a bit...sporadic. 

I also don't think "World Domination" is the greatest of goals in terms of players: Medieval kingdoms were pretty reliant on people just not lying to keep running on a daily basis, and lo and behold, it turns out that noblemen and the aristocracy were very much capable of lying. Having it be an explicit goal on the highest level I don't think lends to people cooperating and being all too interested in really playing things out. 

Now, high fantasy setting where an Empire has [i]already[/i] conquered the world, and as soon as the conqueror dies, the entire empire starts to crumble apart, and you play as factions either wanting independence or to keep this sinking ship afloat? That's a bit more of an interesting take.