holy fire?

[MythicalMino]

ok, i have taken over Marignon (and eliminated Marignon). During the time I was seiging Marignon, I kept getting this message:

"Your undead and demonic troops in Marignon are being struck by holy fire."

At first, I figured this was Marignon's priests (or mages) casting a spell, to eliminate my undead troops (playing as Carrion Woods Pangaea). Then, I took Marignon, and still, that message kept coming up. So, again, I figued Marignons priests or mages were casting it on me from somewhere else. Then, I took Marignon completely out of the game. For a few turns, i didn't get the message. But now, it is happening again...but, only in that Province (Marignon).

Is this a spell that i cannot find? Or, is it a magic site in Marignon (House of Fiery Justice)??

Thanks

Chris