Adept of War

Why is there a blue key? I still haven't figured out where the blue key is needed.

I can't remember after so many years... Although there are two options – either it's for passing to the city in the upper left corner, or for getting some hidden goodies (but there's an alternative way to get them).

I didn't have any video.

Oh, this is the first time I've seen such a bug, and 3.1 doesn't seem to be required here... Do you have a final screenshot?