Themes could include redemption, corruption, the clash between light and darkness, or the consequences of forbidden knowledge. The bonus chapter might involve a side character from the main game needing help, or maybe the player is given a new mission after defeating the main antagonist.
The Warden is revealed to be Elyndra’s cursed heir , trapped in a loop of guarding the city while his mind decays. In a tearful monologue, he admits he orchestrated Alden’s arrival, believing the knight’s "untainted soul" is the key to killing Morgarth.
Potential conflicts: The main conflict is the corruption of the Dark City. Internal conflicts for the protagonist could be battling their own dark past or fears. The enemy might manipulate these weaknesses.
I think that's a good start. Now, structuring it into a deep story with a walkthrough-like structure but as a narrative. It should include chapter breakdowns, character motivations, thematic elements, and puzzle integration. Also, consider the game mechanics—each section of the walkthrough should align with the story beats, ensuring that players experience the narrative while solving puzzles to progress.