Bandai Namco Entertainment went up with the official English trailer for the first Dark Souls III DLC, which is titled Dark Souls III: Ashes of Ariandel.
Ashes of Ariandel will feature a brand new environment with “terrifying new enemies, challenges, and exciting lore to expand the overarching Dark Souls III storyline.”
In the press release they command you to enter the “rotted world” of the DLC, so that sounds about right for Dark Souls.