Deathwing is coming
Deathwing will soon be here, attacking from above, bringing down terror and death onto the unsuspecting citizens of Azeroth.
At random, Deathwing will attack an entire zone and kill everything -- players, NPCs, mobs, creatures and critters. For your death, you get the feat of strength Stands in Fire. We don't know when exactly this will become active on the live realms; however, we are able to confirm it's active on the beta realms.
The full blue announcement as follows:
Once free to terrorize the world, Deathwing will randomly choose territories in Azeroth to attack each day until his ruinous reign is brought to an end. A blackened sky will be the only warning before every living creature caught in his approach is consumed by his terrible fire. The unfortunate victims of his malice will receive a rare Feat of Strength... as well as a repair bill and corpse run.
When Deathwing returns, you'd best keep your eyes on the skies.