There's three significant pieces of DLC coming to The Evil Within, and two of them will form a two-part story campaign. According to Bethesda the first content drop from this new narrative - The Assignment - will land in early 2015.
DLC game director John Johanas explained in an entry on BethBlog how the new focus of the incoming DLC - Juli Kidman - differs from Detective Castellanos, and which parts of the base game inspired the new content.
"We approached the DLC from the perspective that, while Juli is enigmatic during the main game, there were additionally lots of other mysteries about the world and the characters that could be cleared up or hinted at by playing as her. She is a character who seems rather "aware" of her situation, after all."
Johanas continued: "Early on, we listed the things that we wanted to answer and ones we wanted to keep open and worked around that. We definitely leave some of the mysteries open, but I feel we shed a lot of light on the lore of Ruvik, STEM, and the characters while asking (and answering) a whole new set of questions regarding Juli and her mission."
Later on in the same interview the DLC game director offered some insight into which parts of the main game served as chief inspiration to the story-based DLC campaign.
"Probably two of the biggest inspirations were Chapter 5 and 9," Johanas said. "Chapter 9 had you uncover past stories by solving puzzles and exploring and there is a lot of that in the DLC. Overall, Juli's adventure is rather story driven - Juli tends to "discover" these things by her actions and by solving puzzles. But at the same time, the atmosphere and progression is similar to Chapter 5, where you were trapped in a very oppressive area and the "horror" element was at its strongest.
"However, I would say there's quite a bit of variation in her encounters so I wouldn't want anyone to think "Oh, it's just another Chapter XX." Even the "horror" element has a different feel! Juli's experiences are much more dark, lonely, and claustrophobic."
The Evil Within launched on both old and current-gen consoles (and PC) in October, and you can read what we thought of it here.