A lot of the people in my dreams are here, actually. It's definitely nice.
Well, that's the thing. It's sort of his symbol of power. The helm allows him to melt into shadows and pass through walls. Plus, when he wears it he can't be touched, seen, or heard. Which in turn basically allows him to radiate fear so intense that it can easily drive a person insane or stop their heart. At least,that's what Grover said. It's basically why people fear the dark. So, I'd say it's a pretty important item for him.