Just for clarity to the readers, and not to split hairs on words
, I correct Slippery - the ritual he's referring to is "Send Horror", and not "Call Horror" which is a battlefield spell. - This can be used in the same way of Send Horror (and earlier in research IIRC and for less slaves) if the SC is near a friendly province: Teleport in a mage to call some horrors (eventually Horror Marking the guy too), then have the mage retreat in friendly territory.