When someone is a witch satanist and hes says he's marking youwhat does that mean?

Marking someone is to put a curse upon that person. It will play upon the mind of that bewitched person into thinking that they have been so cursed. This will not happen if the person has a strong mind realizing that marking someone is but trickery. The weak minded person believes that they have been marked and so they themselves cause the marking to happen.

The Australian Aborigine believe that their medicine man can "Bone" a person. They believe in it so strongly that they actually bring about their own deaths, unless the imaginary bone is removed by the medicine man.