I really like this idea. I really do. But it definitely needs some polish. First thing, speed it up. Moving is slow, dialogue is slow and I hate to say it, but the slow time mechanic isn't really helping. Don't throw it away, keep it in your back pocket for the next game, It's cool, just not here. Second, minor quality of life stuff, don't limit the y-axis on the mouse. If you don't want the cultists to look like they're falling over, lock their billboard to the y-axis. If your levels are going to be just halls and walls on the same plane, you could also just let the player walk around on the ground instead of flying, then you don't have to worry about the player going into the floor or ceiling, if it doesn't feel ghosty enough put a filter on the screen. That's about it. Also fix level 2, I accidentally de-possessed a yellow cultist in the two lever room and soft-locked myself, because I was stuck in a room without a way out..

I like the possession mechanic, and the puzzles seem interesting, but the glacial dialogue speed was a little grating.