The Worldbreaker (quest)

Objectives
Defeat Deathwing, the Aspect of Death.
 * Aid Thrall in battling Deathwing

Description
There's no time! Deathwing struck before we could form against him. If you do not stop him, the Earthen Ring will end this day!

("Deathwing: You are the only one left who can stand against the Worldbreaker. If you fail, all of Azeroth is doomed.")

Rewards
You will receive: (or  at max level)

Completion
You're awake! Thank the elements. I'd almost lost all hope.

("Yevaa: Nightmares threaten to swarm and consume all within Iso'rath.")