Clearly, the answer is mission gnomes.

How are missions created and what steps do developers go through in placing them in Tabula Rasa? Mission Designer Rebkah Tran takes us behind the scenes and discusses story creation and content placement in Torcastra Prison. Don't miss this insightful glance into designing a prison breakout and the rescue of a downed airman.

In Tabula Rasa there are many steps involved in creating the rich story line of the world. First of all, we've amassed an overarching story which includes lots of detailed back-story the player may never see and branches far out into plot twists and turns that we'll touch on in future expansions. Next, that fiction is trimmed down leaving the content that the player will visit in game. This is then split amongst all the overland maps (the persistent maps that are shared amongst all players) in the game world. Each overland map then links to about three or four instance maps that provide more unique content for individual parties. It is here that we can more intimately progress the story for each overland map.

Read more at Ten Ton Hammer's TR site.