The Forgotten Army

 is a main quest in.

The quest is the introduction for. It's automatically obtained by camping outside the White March, after completing the main storyline quest for — The White Forge.

Synopsis
Upon witnessing a strange army in their sleep, accompanied by hundreds of eyes, the Watcher realizes that they must travel to the White March and uncover its mystery, lest they fall prey to the mysterious army coming down from the mountains...

Walkthrough

 * This is the overarching quest of, whose resolution is necessary for any sort of positive ending. It runs in the background, tracking your progress in identifying the threat and eventually figuring out how to deal with it. This means completing:
 * The Iron Flail: To learn that it's not the Readcerans, but the Eyeless.
 * The Rising Tide: To meet the Eyeless' master and learn the background to their existence.
 * Lair of the Eyeless: The final solution to the problem.