Hmm, I didn't read the whole thread but ... if the level of
horror marking is applied like damage maybe you could make a copy of
Horror Mark that does negative damage?
edit: Found a way to cure
horror mark...
Get a unit
horror marked 65536 times...
So if
horror mark has some kind of damage setting that to 65535 would
remove one level of
horror marking...
2nd edit: how about chaining spells?
Will chaining
horror mark to itself cause an infinite loop and can that be broken (if no more valid targets are on the field for example?)