The entire concept of The Void, one of the potential afterlifes in the Asleep version of Fire Emblem. If you weren't heroic or evil enough to become an einherjar or one of their twisted cousins, you'll relive your life for eternity. So, if you're Anna, you'll relive your twenty-something years of life...then get killed by your future daughter again, over and over for the rest of existence
Its creation - IT USED TO BE HEAVEN. Grima, back when he was fighting with the first Exalt - Chrom's ancestor and Marth's descendant - razed HEAVEN to the ground. This is the first real hint we get of exactly why the Pantheon are so afraid of Grima - he did that even before they reached his level of power.
