John: As opposed to 'imperator' for ruler? Literally 'one who gives orders'.
Whose fluff is valid: Nobody's fluff is historically canon unless I say so, and I am unwilling to say so unless it contradicts the world history in a clear way (such as the dates of the Arcanan Empire etc). Your racial backgrounds are the backgrounds as your races know them, complete with propaganda, mythology and misinformation. They are not gods' truth.
Arcane Magic: I'll let it be a school, but I'll balance it to avoid the Mary Sue aspect. It will be a hybrid school, though, since all of its powers are covered under other parts of the five Prime Schools (Light, Death, Chaos, Sorcery, Earth). I'll cover those later, but telekinesis, time manipulation and teleporatation are covered under Sorcery, gravity/physical forces manipulation is covered under Chaos and divination is under Light/Earth.
Spell of Mastery: The Spell of Mastery gives you control over all magic, effectively putting an end to magic in the world. If the Master Wizard does not wish it so, undead will not function. Non-native fantastic creatures will be banished in the blink of an eye. So much as conjuring an illusory rabbit out of a hat will not function. And it essentially takes the resources of an entire empire to construct the materials and focus points to make the spell work; a single mage operating on his own couldn't gather the resources. The Spell of Mastery will be available as a capstone technology for any of the magic technologies; but it will be absurdly expensive. On the other hand, it will almost win you the game outright.
Plot Devices and McGuffins: Yes, this is my area. Fluff and plot differ - this thread is for you to fill in background and racial heritages/culture. If I am impressed, I might use fluff elements in plot, but frankly plot will be secondary to strategy anyway. I will throw in random events to spice things up and keep things moving, and some of those events will tie into 'plot', but you are very unlikely to ever influence me in that effect. On the other hand, using your racial background/fluff to justify wars on each other is exactly as valid as doing that in the real world would be.
Stability of Alliances: As I said at the start, alliances can be made and broken at will. I will not elaborate on my personal views on why the Western Dominion crumbled, suffice to say that leading an Alliance or Empire takes charisma and a strong reputation for honour or character, as to a lesser extent does membership. In an Alliance, everybody must be able to accept that they have an equal place (even if a more or less equal one) amongst the Alliance. In a Dominion/Empire, everybody must be able to accept a feudal arrangement that works out for them - fealty in exchange for benefits and protection. Alliances can be harder to manage in terms of politics; Empires at least make who is in charge clear, but require charisma and a solid reputation to keep control over. We will see how well this turns.
On Going Too Far: The reason I pushed discussions into this thread is because I do not moderate it, and if they had continued much longer in the game thread I would have had to kick somebody out of the game. There is a point at which the usual grumbling or rivalry that we expect from a game crosses into genuine player enmity (and even bullying), and that point was passed. This way, you don't have to sit through the argument to play the game. But I won't say I'm happy about it. It's simmered down some now, but if it gets back into the game thread I'll kick players and replace them.
On Olde English: I prithee, good sirs, use thy 'thees' and thy 'thous' correctly, for I am most familiar in the speech of the tyme and it assaults mine ears to hear it abused so.
On Winning the Game: Conquest victory is not the only way to win the game. I will accept a Diplomatic/Alliance victory, if all territories are conquered by the players and then the surviving players either agree to unite as a global empire or form an alliance which then wipes out any other detractors. There are some Megaproject victories; the Spell of Mastery is an obvious one, others might exist. These will usually take several turns to build/take effect, but will either win the game outright or provide such a massive advantage that a Conquest victory will be forthcoming. I don't have any other victory types planned, but maybe you can surprise me.