This song sounds quite nice. Really liked the use of guitar here. Gives that feeling of it being crunching time for Nightmare Moon. She slowly ebbs back into Ponyville wishing to give each pony their worst nightmare forever.
The guitar sounds spectacular and was that.... a Sonic soundbyte I heard? Sounded like a 1-up sound slightly slown down, pretty neat either way. The drums have a nice kicking taste to them. The slight use of static makes me think of a TV breaking as well or possibly Twilight Sparkle's house falling in on itself. Elsewhere, Luna rises to the occasion to tame the Nightmares.
The bass I hear is really soothing on the ears as well. Great work in that part.
Overall, great song and somewhat reminds me of The Prodigy.