RPG design 101, the Big 3+1 Questions: What is your game about? How does your game do this? How does your game encourage / reward this? How do you make this fun?
On the note of creating a game that feels like it "gets" Dark Souls, I want to share Ars Technica's review of the Bloodborne card game which they said felt like Bloodborne despite replicating almost none of its gameplay.