A really solid concept gameplay-wise, none of the assets feel out of place, the audio is convincing too (apart from the footsteps bug), and the visual effect when you rest are really cool. As said by others, the learning curve is really smooth for the puzzles, however, i think you should have teached the dash, and even the basic movement, in a safer environment, but it's a nitpick really. The controls are really not ideal, the dash and the attack should be relocated, preferably on the other hand.
The movement feels really fluid and responsive (maybe the dash is a bit too "smooth", some pause in the player's movement before or after the dash could make it a little more impactful, or even a micro-pause in the game's time). Also, the round bottom of the player's collider has a tendency to slip off ledges, it's not that annoying now but it could be for more tricky platforming sections. I like how you explored the main mechanic, and i think it has a lot of potential, i especially liked when i had to rest twice in a row to use the door opened by my first "ghost"; it felt a bit like inception lol, maybe you could have special benches for the "ghost" to create another "ghost" of himself?
Bonus point for the flag noises and the visible prop behind the last door, it's a subtle and organic way to motivate players. Same for the text going progressively from tutorials to hints to questioning life. Also, the souls vibe is pleasant.
In conclusion, i am eager to see what you will do with it in the future!