So, as it says, what is one really like? I've heard stupid (IMO) stuff that describes it as being anchored into your cranium, covered in crystals, and such, but I've seen SM Librarians wearing them, and they are often shown as part of the armor. Space Marines have times where they don't sport their armor, so how would that work? I'm a Psyker whose powers have great reach. Why can't it just rest on my head, and react to my will?
How attached to one is my character, Primaris or Librarian? In my grand equip scheme for a high-ranking Primaris, the hood is on the list, along with the other "cheesy" things. In this scenario, the Primaris is with a separate group that got their Vendetta shot down, and he was unconscious when captured. The Dom forces sequestered him in one of their city's former Black Boxes, where they once held Psykers for the arrivals of the Black Ships. The group of players have to retrieve him, if possible, but he was stripped of his gear before he woke up, and it is someplace else. Some of it is write off able (his carapace armor, flak coat, and plasma pistol), but his Force weapon, hood, and refractor are a bit more cool, and he's on-loan to their Command staff from an Inquisitor, so he can tell the group "we need to steal back my things". If captured, could they have removed the Hood, to put it in storage? Would it have broken in the act, or killed him? In a Psyker room, he can't channel, and thus it's sort of a moot point (the hood) anyway, but if they wanted to confiscate all his stuff, it would likely be among them.