RWBY

[OpMegs]

Going back to rewatch the episode, it depends on the relative heights.

Our first major size comparisons come when Yang jumps into the Nevermore's mouth (and the fact she can says something about the thing's size).



In fact, with its beak mostly open, it seems she could nearly stand all the way up inside it:



Going by the official height chart from Monty's Facebook, Yang is 5'8" and change, not quite 5'9". So the Nevermore's head is at least, by my visual guestimates, six foot around at the tallest point (top to bottom).

Then we have another side by side comparison with Ruby during the lead up to the kill:



Ruby is, admittedly, tiny (5'2" with boots on), and the angle's rough, but Crescent Rose gives us a little bit more of a reference.

Either way, I'd wager the Nevermore's head from these shots is probably around or slightly smaller than the size of the average jet fighter cockpit. From there you can extrapolate based off the official model.

Just as a rough guess, I'd call the Nevermore 50 feet long from nose to the base of the tail (where the model cuts off in that image). Probably 100 feet all told if you count it in, given the tail is as long again or longer than the body.
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"Oh, silver blade, forged in the depths of the beyond. Heed my summons and purge those who stand in my way. Lay
waste."