Really liking the atmosphere, and I like the careful deliberate movement of the main character, it has a nice feel and feels accurate for someone wearing heavy armour. It feels like this has a lot of potential, and I'm interested to see where it's going. I also like the fact that despite being a knight it is not primarily combat based (in fact I didn't come across any combat, possibly I missed a combat encounter), and the lack of a weapon helps increase the feeling of dread.
Now for some criticism:
The text needs to be more legible. It needs something to make it stand out otherwise you just end up squinting at it half the time. Maybe an outline to the text? Or a darkened partly transparent box behind it to make it stand out from the background?
I think that the level design needs some tweaking. Initially once you leave the dungeon, you have a lot of different paths to choose from, but they all basically lead the same place, and there seems to be no benefit to exploring them all? Which then teaches the player that exploring is a bit of a waste of time, only to later find that there is a benefit to exploration as you can find more fireflies and interesting events, so you're giving players mixed messages.
For a game that seems to be promarily focused on exploring, it also feels weird to have such frequent and multiple points of no return for each section, which for me at least made me worry that I might not have explored everywhere. this might be the point, but personally I didn't find that uncertainty very fun? And it made me reluctant to want to retry the level to go back and find things I'd missed, especially as the lesson that I'd learned as a player early on was that sometimes exploring is a waste of time. Personally, I feel like these restrict exploring, rather than encourage it, so if exploration and finding out stuff about the state of the world is the purpose of the game then I would heavily recommend considering how your level design affects that.
(Also, the bit where you choose to make camp is unclear that making camp means you can't go back and continue to explore the rest of the paths.)On a separate note, the introduction sequence also has some nice atmosphere, but I think that A) it needs a little bit of work on the character animation and B) given that the character faces aren't particularly expressive, having the main character open their helmet to show their face kinda works against the emotions that you're trying to instill in the viewer , so I'd recommend just keeping the helmet on. Let the bodylanguage and voiceacting do the heavy lifting there.
I'm sorry if this feels negative, but I do see a lot of potential in this game and I'm giving this feedback because I want to see it fix these things in order to live up to that potential