What does it mean "even though I walk in the valley shadowed by death, I will not fear evil for you are with me" (Psalms 23) This is talking about someone who sleeps in the shadow of a single palm tree, or he walks in the shadow of the moon. (Psachim 111a)
What we mean is that the demons are scared of the light of the moon, and they hang out in the shadows behind the walls. And if you walk in these shadows G-d help you. But this is only at the end of the month when the moon is in the east and you have a western shadow, but in the beginning of the month (Eastern shadow) it's not a problem. (ibid) I would have had something good if Halloween would only have kept the lunar months.
If you would like to see demons, take the placenta of a black cat, the daughter of a black cat, the firstborn, the daughter of a firstborn, and burn it. (The placenta) Take some of the ashes and put it in your eyes and you will see them. (Brachos 6a) You must keep your mouth shut while you do this. But anyway, I really don't recommend doing this, because you will definitely drop dead from fright. Even a big rabbi did this and he got damaged. His friends had to pray for him to get better. (ibid) Now this rabbi was no push-over. He was great enough that the angel of death used to shmooze with him (The end of chagigah 4) and still he got damaged.
The angel of death himself is very scary. He is full of "eyes". (Avoda Zara 20b) Try to make a big doll full of eyes and you will see how scary it is. When a dying person sees the angel of death he shakes with fright and he opens his mouth. And that's when the angel puts a drop of mora in his mouth, and that's the end. (ibid)
If you do manage to make these ashes and you want to put them in storage, you must put them in a metal flask and seal it with a metal seal, otherwise the demons may steal it. (ibid)