Wow! Your free verse is just magnificent.
Before I throw you roses and laurels, I do want to express my concern at the punctuation. At the beginning, you used a lot of periods, which made the rhythm very jerky. It's fine for the first line, but I think a semi-colon would have worked after the second line. Remember that periods mean a FULL-STOP. So, when you want a more even flow, periods aren't necessary.
Okay. Now onto the magnificent imagery and diction!!!!! You somehow capture haunting and depressing emotion, and it really pricked my heart.
I especially found "we cry silent tears and cry silent keens" to be very emotive. I can imagine the pain on their faces, no longer able to have a voice, praying with all their hearts.
And then your last two lines. Generally, I don't like repeated words so close together, but it works so well in this case. It gave me chills, to be honest. Plain and simple: "hope is hope." It cuts to the chase, and says to me that there is nothing else but hope, and its the last thing to hang onto. Very poignant and it struck me very deep. It was an exquisite, yet simple, way to end your poem and gave a very powerful message for me to ponder.
I don't know if poetry has a wide enough audience base for "plenty of feedback," but there's a Poetry Anyone group in the Beta forums you might be interested in, and I'm happy to read and give you my impressions. :)
Your poem brought to mind all the faces of students and teachers who weren't key players, perhaps, but fought and died for Hogwarts as much as those we mourned in the books. There's a simplicity in lines like "This is it, the night is black" that make me think the narrator is young, a student telling his family of what happened, or writing this poem of the Battle of Hogwarts which was read by him or her to loved ones or at a memorial day service years later.
Certain clues throughout, though, "invisible and unseen" and hope being fragile but "not but a ghost" could just as easily slant the poem's viewpoint to the ghosts of Hogwarts. The "family we'll never see again" could refer to those who died in the battle and became new ghosts.
The poem works on many levels, written by the living, the dead, or someone who was living and then died after writing the poem.
At the beginning, you seem to establish the rhyme scheme ABCB with "black" and "back." Afterward, though, the poem shifts into free verse with only the lines ending with "unseen" and "keens" rhyming.
Free verse doesn't rely on rhyme or structure, yet I found a structure that created an effective rhythm with shorter, beginning lines leading to the longer, emotional ones midpoem and then falling back into the shorter pattern for the end.
One line, "We cry silent tears and cry silent keens" is particularly striking, yet I think could have been more so if you hadn't repeated "cry." Keens are wailed and also sung. You could add layers of meaning if you used:
We cry silent tears and wail silent keens
We cry silent tears and sing silent keens
The second to last line, "Yet hope is hope" matches the simplicity of the beginning. It seems a bit pat, though. You might consider a different phrasing, something like:
Yet hope survives
And still we hope.
Thanks for sharing your poem. :)