Well, it was a game just to test the effects of horror seed in which I played both the caster of the spell and the victim
. And after successfully having cast the spell in two castles, I hosted 50 times and checked each turn of the victim nation. A few commanders became cursed by events, but none was horror attacked.
But I didn't move any army, so no battle happened. Maybe is the spell generating horrors during battles only ?
Anyway, I've made a backup of the game before casting horror seed, I'll give it a new try.