So there is a easter egg when you put on the nightfall helmet and the frosted visor, when you look through it you’ll see some type of building, I think it’s a cabin.
It’s probably just some little texture they use for simulating an environment being reflected off all the visors.
I have to watch all the episodes of Halo: Nightfall to see the easter egg.
It’s on every helmet, just easier to see on the front facing flatish visors. It’s been known since day 1 