Well recorded
I think the struggle with most instrumental recording is the ability to sustain quality from the transfer from the tangible instrument to the PC. I was very impressed with the way the guitar not only sounded well recorded but it was also in sync, and was professionally clean (no mistakes). The squeals were nice as well, you obivously know how to play as well as produce good music (especially with it fitting a certain mood.
As a complete song it was really good. It sounded really well equalized and the drumming sounded extremely realistic. The organs definitely started the song off too a fitting mood, which enhanced it's purpose as a song for Halloween. I noticed the "wave" sound you get with the FL plug-ins but I don't think there's any reason that would ruin or make the song any worse.
You're a very good artist and its cool that you can offer Newgrounds your own music as well as interesting covers of others. I've gotta say I'm apposed to most remixes or covers but yours seemed to differ greatly to the original. I liked the way you took it and as you said metalized it, as apposed to just added a dominate base beat (which unfortunately, is what a lot of people call a remix). It's very much like Slipknot's Vermilion bloodstone remix, only the opposite way round, you took a softer song and metalized, Slipknot took Vermilion and mellowed it out big time.
Anyway, sorry to bore you with my opinions, I'm going to check out some more of your music now, you sound like a brilliant artist. Well done on this song, 10/10.
Rayamondo
P.S. Not to spoil it for you but, the number of the beast is 616 according to QI :)