Disclaimer: I will not focus on Art or grammar, unless the latter would make the deck too difficult to understand.
Of the entries I've left a comment on so far, Ebony Ages has honestly given me the biggest pause to think - mostly on how the deck would play in practice.To begin with, I honestly like the backstory blurb there! It might be just me, but I find it good to have more text and background info to work with, and it's fun to add a few more factions to the setting to contend with. Might be a good idea to give a bit more info on what kind of stuff he does in the criminal underworld, however? After thinking about the gimmick and the given cards, I think I like the idea quite a bit as well? Certainly has that big boss feel to it, being a lot more dangerous than most encounters in the book, and the effects manage to be both gimmicky and strong enough to be threatening by having effects for both being destroyed and getting those reinforcements from beyond the Doors of the Death.
That said, I find myself thinking there are some problems with the Plans to Win. I get the impression from the book that the two Plans to Win are meant to be played together, given the synergy involved? That is a lot to throw at players, but not uncalled for with climactic encounters - more, I think clarifying the intention would benefit the encounter a great deal? Further "Cannot be destroyed by any means" is cautioned against in the rules as something to avoid. {Resilient} is there for things that are a pain to get rid of the normal ways, after all. Thankfully, card text clear effects exist, as do card control effects as noted by Yessoan. But the King of the Underworld being in effect always on your field, combined with the effect of the Doors allowing you to take so many cards at once from your opponent is quite the pickle to deal with, particularly if you are intended to get both out Turn 1.
Don't get me wrong, I do think this is really challenging and would make for quite the BBEG! But the Plan to Win could use those clarifications.
As a sidenote, I find it lightly amusing none of the example cards given use the Simple Card moves provided.
Good job!