Well this game had a lot of confusion to it. Also clearly lacks some music.
Nice starting scene and good effort on making a 3D game though. The main mechanics are also quite clever.
A few complaints from my side:
1) The tiles did not help with depth perception. F.e. in the second room it looks like there is a wall you can just walk around, while in reality you have to phase through the grating downwards.
Maybe some other way of lighting the surroundings would have been better.
2) The combat was damn confusing. I can't attack, but I can possess enemies to hit other enemies? The dragon guys can hit me while I am a ghost? You kind of made a level to teach to player that he can possess enemies, but in that level the normal reaction is to just phase past the enemy directly into the exit, so the player would not even notice that he possessed the enemy there.
3) Physics of the jump do not feel good. Jumps too fast, drops too fast.