Ezio returns from the events of Assassin's Creed II to find Monteriggioni destroyed in a single night — the Borgia's assault on the villa that undoes everything the previous game spent building. Brotherhood begins in the ashes of a completed story and asks what the man who built that story does when it burns. The answer is Rome. The answer is the harder version of the same project, scaled up, in a city that belongs entirely to the enemy.

Burning in a day is the event. Building is the game. Brotherhood's structure — the Borgia towers, the assassin recruits, the district liberation — is an extended act of construction inside a city that has been handed to tyranny. Rome was not built in a day and it will not be freed in one. The session establishes the scale of what has been lost and what will be required.