This is a very old view of the inkubus/sukkubus protection
The Hag Stone is a stone with a hole through it, which is believed to ward off witches and the 'evil eye'.
At night the hag stones should be hung on bed-posts to keep away the demons such as the Night Hag, Nightmare or Succubus who would invisibly seek out their sleeping victims.
I collect them on a local beach