Update on the bug I found concerning Xyless's Chaos form:
If you win a battle with Xyless still in Chaos form (dead or alive) the game starts spitting out this error and will continue to do so until you do the following:
1. Get into a new battle.
2. Turn Xyless into Chaos.
3. Keeper her alive long enough to turn back into herself (4 turns)
4. Get out of battle, Xyless will be bugged (missing portrait/character sprite).
5. Remove her from your formation, add someone else.
6. Save and exit the game.
7. Restart your save. Xyless should be fixed and the error should be gone. If not, save, exit, try again. Also make sure that ALL saves that you have that may be during the time when she's still Chaos when the battle ends (dead or alive), will spew out the error, so make sure they're deleted.