You have a bunch of nice mechanics, like locks minigame, inventory and storytelling through the notes. Really nice atmosphere and all those shadows were a great addition to the overall mood.
It was not apparent in my first playthrough that I can use inventory so I went mad, but on a second playthrough I managed to “deny” the Cthulhu. Maybe making inventory a bit more apparent will benefit it a bit, but it’s not a big obstacle anyway :)
Great job, one of the best atmospheres in games I’ve played in this jam!