[Endoperez]

Horror Mark is indeed permanent, but getting it to the levels where it's dangerous isn't easy. Huge amount of Horror Marks, or perhaps that astral geysir spell, and then a Titan who is hit by a huge horror's Astral Hooks (cause horrormarking) might eventually get so badly horror-marked that it would be useless, but I haven't actually heard it happen after Hunter of Heroes was fixed. There might have been other changes to horror marks at that time as well, so it might not be possible any more.