Let me start by saying I absolutely love this idea. My little brother is OBSESSED with HK and HK:SS and I want to play this with him, but it is fairly clear the game needs some playtesting and refining... Please take this as "I really want to help improve this", not "here's a list of why I hate this", I promise it's the first one.
Issues I noticed when gearing up to play, in order from front to back of the book:
There's a way to discover the second set of details about an Area, but not about Folk.
Folk and Areas are said to have 2 Reputation details, but there's no table for that - I'm assuming it's the Adjective table, since that table is otherwise unused.
The Theme table on page 3 (of the combined books) isn't actually the same as the one on page 30. The first table includes Scouts Scribes Smiths that aren't on the second, while the second has Explorers Forgers Performers that aren't on the first. (Explorers/Scouts and Forgers/Smiths are simple enough to conflate, though, I suppose.)
The combat and damage section assumes you're always using a weapon, but what if you only have a ranged weapon and no ammo? Does "unarmed" default to a category? (Without a Ruined Ring, anyway.)
When you fumble while using a Spell Art or Charm, you become diminished... but that word doesn't appear again in the book. The five statuses are awkward, miserable, eclipsed, withered, and compromised.
You start with a weapon. If you start with a ranged weapon, you don't get ammo, though.
You start with a simple charm of your choice, but it isn't defined how many uses it gets, and there doesn't seem to be a default. 3 uses and 1 use are most common in other parts of the book, but they're roughly tied, it isn't obvious which to use for your starting charm. (There is a line in the Architect Crest that makes me think 3 uses is supposed to be the default, but nothing actually says it anywhere.)
You get your Crest's Focus AND one of the options for the Memento, right? The "pick 1 and only 1" is referring just to the Memento options, I think?
The Crest of the Knight presumably isn't meant to permanently add armor or maximum soul, right? You just get the bonus while you're working to fulfill the wish? Armor's pretty hard to get elsewhere...
Two Wanderers in the same party have infinite heart.
The Witch gets two Focuses (or Foci?) rather than a Focus and a Memento. That's fine, although only having a max soul of 1 without Charms makes it a little tough. But they do get BOTH Focuses, right? The default and a choice of the second? They don't have to choose between the two? (This probably added to my confusion about getting both your Crest's Focus and Memento.)
Crafted items besides rough tools (sturdy tools, ammo, and simple charms) don't say how many uses they get.
In Foraging, it says that identifying a flora makes it easier to find again later, but the actual foraging rules seem to make it harder to find more uses of already identified flora.
Charm balancing: I don't expect a mini-zine RPG like this to be perfectly balanced or anything, honestly. But uh... the Simple Charm that grants 1 armor costs a use each time, the Intricate Charms that provide armor either give a flat 1 or mark a use for 2... and the super-expensive Ornate Charm that gives armor just gives 1 with a huge drawback. Sell the Soul Shield to buy THREE Stalwart Plate instead, get triple the armor with no drawback? (Also, the Blessed Bone is very powerful on a Beast for a Simple Charm that doesn't consume uses. With a d4 weapon, that Beast is getting their max damage bonus 33% of the time.)
Potions appear on the Spoils table but aren't defined anywhere. I'm thinking they're meant to be what you refine flora into? (Can refined flora be made into *poisons* instead, so you can inflict effects?)
Very minor but I'm already here: On the Secondary Flora Effects table, 3 and 4 are both Disadvantage on sight, if it's meant to mirror the Primary table there 4 should probably be hearing.
If a Flora can be used as Ammo (result 11 on Secondary Effect table), does it do its Primary Effect to the target? That would actually be amazing if it were a Primary, since so many Secondaries are drawbacks.
Last thing: Besides the overarching goal to reach the Undervale, is there a point to making Journeys besides spending hard-to-earn Bearings and hoping for loot and xp? It seems like Folk giving quests or missions of some kind should be mentioned somewhere.
Yeah, so... I still love the idea, I mean it. I'm only pointing all this out because I'm hoping for a v1.1 :) thanks for making this and also for reading this far.