Imgur user Subject223 applied some serious skills in the crafting of this Dragonborn iron helmet inspired by Skyrim. He used EVA foam, 3D printing (for the horns), and weathering techniques. It all started with a template (he followed tutorials from places like Punished Props):
I made the template by covering my head with felt and masking tape, and then removing it, tracing out the panel lines, cutting it, pinning it to EVA floor foam, and cutting it out with a razor.
Then he attached the pieces with Barge cement and sealed the edges together with a heat gun. He used acrylic caulk to fill in the seams and smoothed it out with a wet sponge. See a few in-progress photos below.
See additional photos of the helmet process in this Imgur gallery.