Harry Potter and The Order of The Phoenix/WMG

Students use a magical telescope during the Astronomy section of the O.W.L. exams.
The book has Harry looking for Orion in June at midnight (It's behind the sun in June, so you can't see it even if you wanted to), and also looking for Venus (which being the next planet near the sun is always close to the sun in the sky and therefore never visible at midnight). The students use a magical telescope which when pointed at the ground can see through anything blocking to the stars (the sun excluded) that would be there.
 * Maybe that was the test...
 * We even have a muggle equivalent now with the Google Sky smartphone app!

The Veil of Death...

 * Is the Gleaming-bale, the curtains of Hell!

Umbridge is part Hag
Is Umbridge of Hag heritage - she seems to dislike children and is even violent towards but maybe would shirk from actully eating one though so she may be half or less Hag and this would also explain her hatred of "half-breeds" as she is one herself and keeping it quiet from Fudge and Co.
 * This...makes a disturbing amount of sense. Besides her general hatred of children and "half-breeds", it'd explain why she was  (unless Hags aren't Always Chaotic Evil here), and why she seemed so profoundly ugly and intolerable.

The Department of Mysteries Level has another name.
What's right after the Atrium (eight-rium)? The Mezzanine! (I work security in a building with a mezzanine. I read OOP on shift when it came out and I pass the sign saying "mezzanine" a few times a night and often think this.)

The desk guard at the MoM was dead.
Harry notes that no one is manning the desk, but that's all. If they would have looked behind and under the desk they would have seen a body there.