As a multi-theme builder, and if one ignores the HUMP, this isn't a bad parts pack, though one really cannot take the design seriously at all, and there are perhaps a few too many dragon wings to score too highly on the parts-pack scale (again, ignoring the HUMP... which is barely a real piece in my books... more analogous to the cardboard background thingys in some of the early Harry Potter sets).
The minifigs are excellent, and that is my all-time favourite barding, because of its versatility. As for the minifigs, I've always had a special fondness for the captured knight because, in my books, he was clearly a Royal Knight (my favourite childhood faction)--given that an identical fig comes with the Royal Knight's Castle (6090), and another Royal Knight comes with the Night Lord's Castle--even though I suppose there's nothing technically stopping him, in terms of fig design, from being the last gasp of the old Black Knights.
Parts: 8/10 (again, I am not inclined to actually count the HUMP)
Playability: 9/10 (the idea is good: lots of figs, a dragon, a prisoner, even a cave)
Design (contemporary): 3/10 (even for the Fright Knights, this is bad)
Design (universal): 2/10
Overall Score: 6.3/10 (C--not a high mark, at all, but a passing grade)