"You can copy memories into crystals, so I don't see why you can't stuff them into crystals without leaving them behind in your head." Mikoto would be a boon to have right now. Her expertise on these matters (or as expert as one can be on lost knowledge) would likely be of more help to Noctis than Era ever could be. "Hades might be able to look into it for you, once he deigns speak to me again."