Cool combination of sounds and textures- Vocals, pianos, reverse pianos, ambience, (harpsichord or some sort of bell like synth?), enveloped by a lush reverb.
One thing I noticed about your mix was most of the audio was that the main elements in occupying the high end was the harpsichord and ambient noises, which gave the made the track a bit unnaturally dark (as in not much high frequencies) for sections where they were not present. If that's what you were going for, then leave it as it is, but if not using an EQ high shelf to boost your high end frequencies by at around 4.5k Hz region would make the track sound more natural.
Composition wise the soundtrack was well written. Mist and Nails had a good patient, mysterious tension to it. One Friendly Intruder was awesomefor a boss fight, the quicker tempo and cascading piano notes made it feel like a escalating conflict. Well done on creating an engaging soundtrack.