The Diablo III: Reaper of Souls location of the Blood Marsh is the subject of a new developer blog on the official community site. The article contains the lore behind the location and an inside look at how it was created by the developers in preparation for release in the Reaper of Souls expansion.
Crafting a treacherous bog to explore as a bridge between two fantastic locations (Westmarch and Pandemonium, the final stage for Act V) could have been a relatively simple, straightforward task. Our designers, however, rose to an unspoken challenge and took the creation of the Blood Marsh a step further, delving into this location both physically and thematically.
Creating the Theme:
The first step in exploring any area's design is nailing down the ultimate fantasy of the environment, or its theme. In the case of the Blood Marsh and Ruins of Corvus that rest within it, the central theme happens to be one that's integral to the story of Diablo itself: blood.
Read the rest of the comprehensive blog on the Diablo III site.