I actually started this idea as a comment to someone else's post. But decided to expand upon it.
Imagine waking up to discover all your exploits were just a dream? What might be? All the other content and expansions were basically What if's ?
You awaken from your long dream, to the sounds of howling wind. Then screams... You look outside and can't believe your eyes. A tidal wave of frost and fog sweeps across the land, from its billowy tendrils pour the armies of undead. The Scourge! The ground trembles and shudders under the weight of the oncoming onslaught. The masses of undead part as the ground cracks open and unholy abominations of terrifying design hoist themselves out to move with frightening speed and fluidity.
A hum begins then grows into a cacophony as a blue glow coalesces into beam of blue green light that shoots into the night sky. Suddenly! The clouds take shape into the visage of Arthas! He cackles, then bellows out. "Now you will truly feel my wrath!"