You should have acted. They're already here. The Elder Scrolls told of their return. Their defeat was merely delay Til the time after Oblivion opened, When the sons of Skyrim would spill their own blood. But no-one wanted to believe. Believe they even existed. And when the truth finally dawns: It dawns in fire. But, There's one they fear. In their tongue, he's Dovahkiin: Dragonborn!
In a single night, the Brotherhood swept in, and whatever got in thier way was reduced to ash and blood. Then, as quick as they appeared, they marched away. The survivors who managed to glimpse at the armored angels of death have since proclaimed that night "The Scourge".