Actually, it locks which side you join, and you can buy the other side as DLC.
All royalty characters, including the Avatar, has the ability known as Dragon's Vein, which allows them to alter the terrain at certain locations on a map.
That sounds like a really neat skill.
Weapon Durability has been abolished, allowing units to keep using the same weapon.
I'm all for this. My favorite tactical game doesn't have durability either, and I was never much of a fan of it.
A new mode called "Phoenix Mode" will be added; just as casual mode, it's meant for those that are not yet ready for the challenges of the Nohr campaign, allowing fallen units to return on the following turn.
...no, just no. Playing Lunatic/Casual is fun in Awakening, but this is just overkill.