[Edi]

Horrors attacking horror marked beings appear as a special attack (like the event when an indep assassin tries to kill your commanders). It works like an assassination attempt. Just try and build the Forbidden Light sometime and slap it on a mage, you'll see a horror attack inside of five turns.

In a co-op game with my friend, his pretender, a Daughter of the Land, got attacked by lesser horror after ~30 turns of carrying a horror mark. Of course, unfortunately for the horror, she was deep within dominion and in the lab forging an item, so she dropped the heavy end of a dwarven hammer on the bugger and went back about her business.

Edi