For those wondering, a Horror Mark is a mystical link between the Horror and it's victim. The power varies with each Horror, but the basic Mark allows the Horror to apply any ability upon or through the victim to a range of 10 miles. It can only apply non-damaging powers for a range of 100 miles. And it can communicate telepathically with the victim up to a range of 1000 miles. These ranges and properties, like I said earlier, vary with each Horror. Some have a limited range, some extend further.
Getting Horror Marked is a nasty, nasty business. Unless you happen to be or know someone exceptionally powerful (equivalent to an initiate grade 5+) who can enter the astral and hunt the thing down, then you are basically stuck with incredible amounts of suffering and pain. Not even death is a sure way to escape, as many of the more powerful Horrors simply raise your body as an undead monster or torment your spirit and convert it into a shadow wraith.