Memorie
Is this one of the common headaches?
I can explain... I set up a scene where a mysterious hooded figure, upon returning to a familiar location way later on in the game, if players felt like it, and a cutscene happens. This hooded figure would have tried to cast magic on you, but the battle commences before the player character, which is used in the scene, begins the first flash. After fighting the figure, and winning, the hooded figure would use magic to destroy the location the player character is in, therefore escaping said area instead of stopping the spell cast. However... This happened.
btw, this is possibly the only optional boss I'm going to "leak out and reveal" myself, as I've haven't actually gotten to the point when players have the ability to attempt to fight this optional boss.