Add a new section called “Horrors”. Within it, add:

Whenever a Stamped Mission’s Secret Reward is “Eldritch Horror”, if one or more of its Participants is a Cultist, one randomly selected Cultist of those (chosen by the Expedition Leader) is now also a Horror. The Expedition Leader shall make a public post which states which Explorer has become a Horror when this happens.

A Horror may spend 5 Supplies to Attack an Explorer which is at their same location. That Explorer gains 1 Insanity.

Horrors are not welcome in Camps, so they may never enter them, and if they are within them, they are instead placed at that Camp’s Latitude.