How to complete A Light in the Dark quest in WoW The War Within

Completing the following four previous chapters of the main campaign storyline in World of Warcraft: The War Within will start the "A Light in the Dark" quest. These are as follows:

Chapter 1: Against the Current

Chapter 2: Ties that Bind

Chapter 3: News from Below

Chapter 4: The Machines March to War

Once completed "The Machines March to War," head to Dornogal and speak with Allerica. She'll send you to the Aegis Wall in Hallowfall to speak with General Steelstrike. Note: if you weren't able to pick this up prior to today, it was time-gated and opens on September 3rd with the weekly reset.

I won't go into too great detail in order to avoid any spoilers. Essentially, after discussing things with General Steelstrike, you would complete a few preliminary quests and then get the quest "A Light in the Dark" from Anduin Wrynn. During this time, you will pursue and defeat the main antagonist of the expansion.

Once you've finished this quest, go back to Alleria Windrunner to turn in the "A Light in the Dark" quest and to finish off the endgame campaign questline for The War Within. Provided that you've done all of the other ways to unlock the Earthen Allied Race, you'll finally officially unlock this option.

Accomplishing these steps and completing the "A Light in the Dark" questline serves to progress one through the story and allows the unlocking of the Earthen Allied Race, opening new opportunities and adventures within World of Warcraft: The War Within.