2 small questions about horror mark

[Sheap]

Being horror marked mostly just encourages horrors in combat to attack you, it doesn't draw that many horrors by itself although it can happen. If you're doing something that encourages horror attacks, like casting spells in Astral Corruption or living under a Dome of Corruption, a horror marked unit is more likely to be on the receiving end of the spell, and is more likely to get a meaner horror.

I'm not sure if being in magic dominion increases the odds of horror attacks or not. They're so rare it's hard to prove it.

Some horror marks are "worse" than others although it doesn't show it. The one you get from the spell is relatively mild.

Lesser Horrors are extremely feeble and can easily be defeated, but if the horror marked unit is extremely weak they might be able to kill him before they are themselves destroyed. "Normal" horrors are strong enough to wipe out most mages or national commanders and Groups of bodyguards unless they are SC's. Doom Horrors and Kings of the World rarely appear unless wished for, but there's not much hope of defeating them.