DUSK had left due to "problems" in the outpost in terms of leadership struggles among the populace, toward the entire community, slight food shortages (over the time the story takes place and before, less food was found and also the coming of winter meant less food.)
The coming of the "New" infected and their constant assault on the outpost
The sudden appearance of Military outposts positioned around the city, although all have been searched and confirmed deserted.
They believed the spirit of Draconis would lead them to a better place of safety, and security, and so they set off with all possessions. Exactly 2 years later after they find themselves in their new outpost (still gotta decide, where ever you guys want it. its your choice.)
Also Applications may be set now so you can reserve your spot in the story.