If you want mystic and occult, look no further than the piano music rendered by Rosemary Brown, who allegedly took dictation from Liszt, Chopin, and company. Was a modest sensation back in the 60s.
Ligeti wrote plenty of creepy music - Atmospheres is enough to make anyone's hair stand on end.
You want creepy orchestral music: check out the symphonies, any of them, by Humphrey Searle. Weird, scary and interesting as all heck.
Howard Shore: I read somewhere that his soundtrack for LOTR is considered to be the greatest soundtrack of all time. Really? What criterion? Better than anything of Korngold, Waxman, Steiner, Herrmann? I love the movies, and the music is quite effective and adds a lot. There's even a well produced book all about the score. But...the soundtracks don't stand up by themselves outside the movies. The cds are rather boring. Even the LORT in Concert that was making the rounds a few years ago taxes the listener. But there are scores by the masters of Hollywood scoring that make great concert pieces.