Destroy 5 Tormented Spirits.
These spirits must have been released when the tombs were opened...
Death was not final for the Mogu. Instead, death was merely a stop over on the path to a new body. Spiritbinders used a foul magic to transfer spirits from one shell to the next.
Years of being trapped in the tombs has left them confused. They need to be destroyed before their confusion turns to anger or worse, they find a new shell.