I've had to find all this out online, since the characters in-game make only passing mentions of it and never really explain anything.
But I still have questions:
-Who/what are the Thalmor? It seems to me from the information that they're either just Altmer, or an Altmer-Bosmer hybrid?
-What are they and why did they suddenly get the power to take half the Empire? Even in a weakened state I can't imagine a single province or two being able to take over so much land and sack the Imperial City.
-Where are they from?
-Why did they want to outlaw Talos worship so much?