[Edi]

The only things that can counter horror attacks are basically having some sort of meat shield surrounding the god so that there is no room for the horror to reach him first. Then a barrage of high precision spells like Incinerate, Soul Slay and such, but if the spells can be resisted, you need as much penetration as you can get from high paths and items.

Horror marks do not go away at all. As for how you got a horror mark, it's best to stay away from situations where you could get one.

Edi