TLDR: Whether it's woo or in your head, confront your fear! Get comfortable with it and it'll become less scary.
Meeee! I used to get intrusive thoughts, especially when I'd go for a pee through night and pass the top of the stairs. We went through a patch of really weird, creep stuff happening and eventually it came to a stop when, after a particularly freaky occurrence happened to a family member, I went into the bedroom and said out loud 'this needs to stop! You're scaring us and we don't want you here!'
I felt like an absolute headcase but it worked. Even though the children didn't witness that, they said their bedrooms felt better the next night. Regarding the scary deep, dark, staircase, my dog often gets up through night for a pee. Great, just what I want to do at 3am. I started going up the stairs really slowly, getting braver but still feeling like something was behind me 😬 now I can use my phone light alone and go down, can go back up in the darkness. The feeling is still there but I think we need to face our fears.
I'd try going back in there for a night. Talk to your fear/the demon 👻 in your head and tell it to go away, it's not welcome. Look into the darkness and rationalise the dark corners/shadows. Though, after I confronted mine in my loud voice, my partner slept soundly but I couldn't sleep. 100% expected to see a face directly infront of mine for hours afterwards, thinking it's not going to be happy with me 😂 I was wary to close my eyes for too long 😂 but, face your fears, nothing came seeking revenge against me (thankfully 😅)
On another note, I used to have a recurring nightmare. It was petrifying and I'd wake up scared-stiff, literally. But after the previous time of confronting the thing out loud in real life, I felt empowered and when I next had the nightmare, I shouted back at the creepy voice and squared up to it. Never had it again!