I really enjoyed playing this puzzle game. The puzzles all felt good, and even if the answer was not at first clear, they all made sense after I understood them.
I do not trust the soul recycler very much. They make me think of the fae, and give my the "what did my character just sign up for" vibes. Thinking in that regard I think that the character made several flaws in dealing with it. For example how long will they be doing the soul recycler's job?
For the fire puzzles I think that there needs to be a greater difference between burning posses-able skeletons and burning smashed bone piles.
Being able to posses the mimics felt a bit odd. I don't usually think of mimics as being undead but maybe they are mimic corpses?
I think my favorite of the full game mechanics was the skeleton snake which looks cool.
I like the pixel art aesthetic. The trapped souls look and sound good. I think it would be cool if you had a different track of music for each area in the main game but the track that you have is good and I think would work the the whole game.
Bugs:
You can get locked into moving in one direction by pausing while moving. Your character will be moving in the same direction while paused and when you un-pause you will not be able to move in the opposite direction.
Your Portrait image shows the character with the lantern before they get it.
-T