Awesome stuff! You really nailed the atmosphere. I finally got through all the decks on hardcore; it was a fun challenge! I'm starting to feel really bad for THE IMP... Really excited to see what comes next; I would totally pay for an expanded version of this!
Wanted to mention a few recurring bugs:
The codex still reads "You have not used this deck yet" for all decks except the Starter Deck.
Lucky can trigger while returning a card, but it gives the card that would have reached perfect before returning the card.
The "small upgrade" chapter displays 1 and 2 as options for "THE MASTER's DECK," even when you don't have any.