Tartarus

MacArthur, “Tartarus, which in Greek mythology identified a subterranean abyss that was even lower than Hades (hell). Tartarus came to refer to the abode of the most wicked spirits, where the worst rebels and criminals received the severest divine punishment.” [John F. MacArthur Jr., 2 Peter and Jude, MacArthur New Testament Commentary (Chicago: Moody Publishers, 2005), 85.]