The first gem (the question mark) is equivalent to the question mark gem in English Alphabet Lore; it was supposed to be A's, but then was passed into Q who showed it to all the other letters. It shows the future. The second gem (the inverted question mark) is Q's own unique gem he cries out shortly after he sees the future happen via A's question mark gem. It shows the past. It only appears in the second epilogue, but It's also supposed to appear in iZ because Q cries it by himself. The third gem (the inverted exclamation mark) is an extremely powerful gem that can heal, revive, and give its user all power. I thought it was supposed to be I's gem. It only appears in the second epilogue.
