This piece is very good. You really nailed the feeling of fear of the unknown. A good idea for you to incorporate into your future music is the use of clashing notes. In music people typically avoid using notes that would clash with the harmony. But you can see people using this feeling of discomfort that clashing notes cause to their advantage. https://www.youtube.com/watch?v=dA3mccI1DjY. We can see in this song by Junichi Masuda and Go Ichinose that they use odd notes in the beginning to create a feeling of suspense and unease. But this style of boss battle clashing is good for songs that start off slow. For a clash in the chorus, I'd recommend https://www.youtube.com/watch?v=zxz3DP8v9ko because of its use of clashing. I see that you did a bit of this clashing in the later section of the song but I just want to reiterate this idea of purposful clashing because it's a really good skill to have under your belt. I really love the creepy demonic feel you bring towards the end. You really set the atmosphere well. Keep it up!