Chaos Isle has at least 1 update beyond my playthough. Somethings may be outdated.

The mod is great people should try it. However expect some stumbling points where you go to the comments for hints.

World design:
The world does a good job of guiding the player to each area. The progression feels natural. It was also nice that area boundaries had 2 entrances/exits. That extra option made travel easier and feel better when breeching the unknown.

Given how hard some puzzles / secrets were, I am glad each area could be more or less completed before moving on to the next area. That helped narrow down the puzzle space.

I also like what you did with the Hub. It was creative, allowed a puzzle with the figurines, and also worked as fast travel. I especially like how there is an opportunity late game to get a bird's eye vantage of the Hub (I wish the circumstances and duration were longer but ...).

Dungeon design and mechanics:
I loved it. Most of the areas intertwined 2 layers, and they did so to great effect. As usual each area felt unique but you did a great job driving mechanical uniqueness. The two areas that were the most similar were the NorthWest and the East. Each of the areas was thoroughly enjoyable to explore.

Navigation Stumbling Points:
Early on there is a trapdoor between two buildings. Later there are times you need to cross small gaps, or dig down, or crawl under a low arch. These puzzles can be significant stumbling blocks but are also good puzzles with a bit too little of clues. I suggest players be willing to read the comments to see when other players asked for hints and received them from other players and/or the dev. For the dev, I suggest maybe adding a couple more in game notes as clues. This is in contrast to the floating platforms that appeared when you stepped on them because those were better telegraphed.

Secrets:
Some of these are hard. I am glad I asked in the comments for hints when I needed guidance. In the end I had 62/64 secrets. It gets easier as the player starts to gets a feel for the dev's secrets.

Digging:
The lower quantity of notes / hints and some of those navigation stumbling points had me digging every tile in some areas. A couple of times this resulted in my digging where I needed to, but not how I needed to. This was related to crawling. Thus I was given a false negative saying digging there was not the solution. This was a bad habit the map was training me to do. It resulted in me finding some secrets before any hint was given. On the other hand it also let me find a few secrets than I never found hints for.

Respawning Monsters:
I think you stuck a good balance with these respawns. They worked as a good way to add variety when someone is traveling back an forth investigating a secret. Those moments of interruption were sometimes helpful to reset and think about the problem again. It was also a good idea to limit the respawns to when a player was changing zones. We can still make a place temporarily peaceful if we need the peace.

Armor:
Most armor sets have set bonuses. I really liked the Mirror Set's +10 Resist All. However the 2nd half of armor only get to complete their sets near the very end. In practice most armor sets are obsolete before you can see their set bonus. I suggest making some of the more mid armor (example: Plate, Valor, Rogue, Lurker) be spread out across fewer areas. That way a player has to choose between Plate set vs a mishmash of some Plate and some Meteor/Crystal.

Herbs vs Alchemist:
I found less than 10 of each herb. Without an alchemist, I found that to be too few for me to use before the final fight. Since potions of healing are so scarce (I could only find + brew 12), I exclusively relied on using a crystal of life or reloading to deal with injured body parts. This also had a cascading effect where I never brewed antidotes or antivenoms because the Etherweed and Bloodcaps were too scarce. On the other hand, the world's balance, with 1 avoided exception*, never forced the issue because backtracking to a crystal of life was usually an option.

* Bring potions of healing into the North West. A foot injury in the ne corner of the NW map can force a reload.

Character Progression and class tweaks:
My party reached 13th level without farming. Humans were able to get to 14th with the help of the Spirit Amulets. You also provided 9 tomes of knowledge that I could find. I think that was enough for good build variety and complete character progressions. Even my backline melee rogue warmed up to you bumping reach to Accuracy 3 :).

I liked the Fighter changes since they helped let the scythe shine. You even gave the scythe reach. It is my favorite weapon but it is often obsolete late game.

I also need to try out Firearms on a later run (and I will be replaying it again sometime) since there seemed to be enough ammo.