15? That's seems very little though it explains something. Thanks.
I have changed the setup and even got where I wanted.
Changed Swarm - 17 dragonflies with ranged horror mark attacks with 15 ammunition and negative reinvig so they are immobile after round 15, a commander with illithid paralyze that dies from fatigue at some time. When the leader dies, the dragonflies start dying, too.
Now I horror marked a dragon several times and cast that spell on him. His horror marks where completely gone (so maybe even remove all horror marks no matter how high) and he wasn't attacked by horrors.
Interestingly he was immune to horror marks after that.
Looking at the battle the following thing happened. First the dragon was paralyzed and then hit with horror marks. Horror mark icon is still there.
After some rounds horror mark icon was gone and the graphic of the horror mark weapon changed. It stayed away for some time and then it appeared again. So maybe there's a window that you have to hit, maybe it screws the whole game, but hey, that's wild magic.
