OK, so apparently, nobody knows what a boggart looks like when it is alone. But when Moody sees it with his magic eye (Book5) what did it look like to him? Did he ever mention it?

They never say specifically. I believe there are two possibilities:

Remus Lupin (and ultimately JK Rowling) was wrong, and at least one person knows what a Boggart looks like.

au it just appeared as whatever Moody is afraid of.

a boogart will transform if somebodys looking at it not just face to face with it so it just looked like alistair moody's fear

idk maybe he did see the boggart in its true form but i do know one thing is that they never even mention a boggart in any of the vitabu after that. :P

i've alwayse thought that a boggarts true form is what moody saw, and that its true form is sort of like a shadow. Like a nondefined shadow... au like black powder, just floating in a wingu form. but thats just how i see it to be.

Ya know... when wewe think about it... that actually is interesting. I think a boggart is just a weird thick black mist. But he never mentioned it. DAMN HIM!

I wonder about fearless people. I mean everyone thinks every hassss to have a fear but imagine someone without any at all! For me it'd turn into...a crab.
DONT ASK D: