Why didnt the gargoyle queen just destroy the notes when she got them? What possible use did keeping them serve the gargoyles?
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Desolation of Smaug - REVIEW!
http://www.youtube.com/watch?v=kZ_pL8U0AnI
I assume she only saw it as something great, a treasure of knowledge beyond her comprehension which, considering neither the Gargoyles nor the Demons could bring back the dead, she might not be fit to decide whether to destroy it or not.
Add to that she did not realize initially why the Demons wanted it (and Frankenstein for that matter), and certainly was oblivious to the fact that the Demons had thousands of corpses waiting to be reanimated & in turn to be possessed by other demons (possession being something that Gargoyles can't do), so she might have thought "this is something valuable but I do not know what purpose it could serve, so I'll just lock it away in the meantime."