My guess is Post Meridiem
Seeing as how you had Rose at Twilight, my guess is the meridiem is referring to midnight. It's a very dark and heavy theme that I absolutely love. For those who don't know what meridiem is, think about that A.M. and P.M. stand for. If you're lazy:
"The 12-hour clock is a time conversion convention in which the 24 hours of the day are divided into two periods called ante meridiem (a.m., Latin: "before mid day" English: "before noon"] and post meridiem (p.m., Latin: "after mid day" English: "after noon")."
Thank you for adding yet another awesome song to your collection NemesisTheory. You never cease to amaze me.