Very cool read. I love the monsters, magic items, and that some problems have no written solution; best for the players to figure it out. Time shenanigans are fun as well (even if they can be a little tricky to run) but I think Shadowdark would be a good system for this because you could just use the Torch Timer mechanic to make it work.
Some nice evocative ideas here (the water making you thirstier is great) and the cover is lots of fun. Great job!