This is actually pretty simple if you follow what i'm about to walk you through:
1. You want to dump your Fate's save file using a save file extractor: JKSV (highly recommend this), or SVDT etc.
2. Now you go and grab this tool by RainThunder that will decrpyt your ChapterX save file:
https://github.com/RainThunder/FEST/releases/tag/v1.1.1
3. Go into the directory of your dumped save. You'll find several files depending on how you used the game. MAKE A BACKUP OF THE SAVE FOLDER IN CASE YOU MESS UP. Drag the ChapterX you want to decrpyt onto the executable of Fire.Emblem.Save.Tool (FEST)
4. Now with that decrypted save file (ChapterX_dec), you want to open it in a Hex editor of your choice (I recommend HxD)
5. Now I will show you how to find and edit each unit Chrom, Frederick, and Lissa:
Chrom: 06 81 00 00 is apparently the working value according to another user, so ignore the one in the screenshot
-Follow the Chrom picture above for Frederick, and Lissa.
Frederick: 00 0B 14 This is wrong, will correct later
Lissa: 0B 00 14 This is wrong, will correct later
6. Save your changes, drag the chapterX onto the executable of Fire.Emblem.Save.Tool (FEST) again. Now your edited save has been encrypted and is ready to restore
7. Restore the edited save from the directory using your save file extractor on your 3DS
8. Boot up Fates and see if it worked!
Note: I may or may not have seriously gotten the character IDs severely wrong. I only tested one save file. If you can find the character sections for Chrom, Frederick and Lissa my guide will easily point out the shield location you need to change. Remember always backup your save before making modifications like this. If someone of higher knowledge would like to point out a mistake I made, please do so! Any further questions for me regarding this guide should be sent via PM, that way we can discuss one on one easily. Big thanks to
@RainThunder for the FEST tool, obviously
@DeathChaos25 for making the DLC, and whoever created this extremely helpful resource:
https://docs.google.com/spreadsheet...Z7ddenFSURmw/edit?pref=2&pli=1#gid=1077677946.