

Instead of being built for protection, Zero had the helmet designed so he can conceal his identity while still being able to use his Magical Eye, which needs direct eye contact to work (facilitated by a hidden panel on the mask opening with the push of a button). Unusual in that the actual faceplate has to be removed by hand after the rest of the helmet retracts into it. We only know thanks to development material. Although it's a downplayed example, because in the entirety of the show we never actually see it do this, as he's either wearing it or not wearing it but is never shown donning it on or taking it off.

It operates by using Applied Phlebotinum, Functional Magic, storing components in Hammerspace, through Impossibly-Compact Folding, or maybe just a Hand Wave. And then they reveal themselves with an unbelievably cool helmet that just slides, clicks, folds and does all manner of other mechanical origami. Picture the scene: the character is wearing their Powered Armor or other such suit. For them, there's a simple solution: the Collapsible Helmet. Heroes or villains who avert Helmets Are Hardly Heroic still rarely want to bother about putting it on, or removing the helmet and carrying it along.
