When you're a city girl and suddenly hole up in a house in the forest for a week, stuff happens to your brain. It did to mine, in any case. It doesn't much matter whether my poor brain was trying to entertain itself, or having temporal lobe hallucinations, rehashing cultural programming, or tapping into the multiverse. What was interesting was the process itself. I started seeing things. By that I mean getting quick visual flashes of what my brain imagined might happen. Now, that happens on a regular basis anyway - for example if I'm climbing a steep set of stairs, I get a flash of me slipping and crushing my face on one of the steps. Or carrying something heavy, I see myself dropping it and crushing my feet or someone else's. I reckon it's the gnomes in there doing risk calculation. It would however appeal more to the imagination to think that the multiverse just spawned another little universe, and I get a glimpse of what happens in the other timeline.
So, I started almost-seeing things when in this forest house. Drawing the curtains at night, a quick mental image of a face among the trees, enormous round eyes gleaming. Or worse, an image of those eyes rushing towards me, trying to reach the window before the curtain closes. Walking past a darkened room and momentarily seeing a humanoid shape in there. Waking up in the middle of the night, absolutely sure that someone was standing outside the window. And when you're half an hour's bike ride away from the nearest village, someone standing outside the window is not a very good thing. And somehow I knew that this someone had a maniacal grin on their face, I knew where it came from, and I knew it was malevolent. It was very difficult not to believe this was true. It was terrifying, but also exhilarating - like watching folklore in the making, first-hand.
Things had calmed down by the end of the week. But it's not so difficult now to put myself in the shoes of those who might have lived in the same area a century or so ago, and who would have sworn they saw the vittra or some other creature staring at them from the forest's edge. And the story would bloom from there.