Anyone notice that the behemoths seem to have mechanical devices implanted in them? Shown here:
Odds seem pretty good that this is how Niflheim is controlling the behemoths and perhaps their other monster soldiers as well. As you watch the trailer, you can see that the striped behemoth's machines crackle and flare with energy that I assume is magical. Machines produced by the stolen crystals, or pure works of science? Interestingly, behemoths without stripes seem to have embedded machines that don't glow, making me wonder why the striped behemoth's are in the first place. Has it sustained damage, or has it activated as some sort of booster for the behemoth? Are the striped behemoths special in some way?
An example of a behemoth without stripes and its latent device:
I'm not seeing machinery like this in the iron giants, but I'll take a closer look down the line. It might just be hard to see since the iron giants themselves are made of metal, or they might not require them for some other reason. Thoughts?
Edit: Forgot to mention that if you watch the trailer, you can see that Noctis' reticule targets these as one of the attackable points on the behemoth. If it's a control device, the repercussions of destroying it seem both obvious and hilarious.