I finished the game, er, demo, I guess? The boss fight felt lacking. Just more health, spellcasting, and so on. Also, it wasn't all that difficult of a challenge. Maybe the boss has certain moves which seal your actions for a few turns? Have "Cough Medicine" to regain the ability to do spells? The first few fights were difficult because I was managing my resources and using Guard to regain my few precious hitpoints. Replicate THAT feel throughout the game. I also enjoyed the limited fights, and the reward for searching, though sometimes when given a choice (like after I've approached the stalagmite) the following choice was irrelevant. Give me a choice to use an expendable item to "scare" (or something) the threat away, or go straight into the fight after I've approached the stalagmite.
The last sequence played out like a movie. Now, I've no idea how to do this, but, here's maybe an idea for "quick-time" events. (If you even want these in.) When the player searched, at some point a text box would show up. Perhaps, have a text box show up with scrambled (if that's even possible) choices, and give the player like 2-3 seconds to select a choice. I know there's code out there on how to construct a choice box outside of what's in the Events : Contents : Event Commands options.
Also, I feel like it needs puzzles, of what type, I'm not sure. The basic one would be a stone door which requires some type of password. Perhaps, have hidden "letters" throughout the room, Though, since I've never done a text-based game, I'm not sure what to suggest beyond that.
The minor status afflictions by the creatures, especially bleed, kept me on my toes each fight even when they couldn't deal damage to me any other way. And the horde of enemies did stop me from rampaging through battles. The spells might need balancing (fire worked better than poison, and seemed to deal a lot more damage and last more turns even though it cost less.)
You have exploration down pretty good, and I do admire the descriptions. These are just minor ideas, and I don't want to overburden you. Initially, I was "great, a text-based game. They must've thought it would have been easy to do." But, I will wholeheartedly admit, I was sorely wrong. The first hook was the battles. The little descriptions of the creatures, and even the tutorial to "use my imagination" seemed to fit the atmosphere you had started building.
Ah, environmental hazards. Mushrooms which cause "confusion" or the like. Maybe they change the available options? I liked that I could buy rope, a consumable, story-necessary item, and that it competed with healing items. Although, the potion gave me a Chekhov's gun by stating "it could heal someone" and I thought I needed it to heal my friend to get the "good ending."
Sorry, I've suggested a lot. I'm an idea-generator without an off switch except when sleep summons me.
(If I need to summarize anything I will. And good luck!)