In my latest game Lord Verga of the Yithril declared war shortly after meeting me.  When his army crossed into my borders I tried casting Wither, Freeze, and Tremor to either delay their advance or weaken it a bit.  I got the following message, "Target is protected from offensive spells."  Can anyone explain why that is?  I looked at all his equipment and traits and none of them said anything about magic immunity. There was an ophidian in that army which is immune to magic but I don't think its immunity should extend to the whole army when on the strategic map.  Do the enemy sovereigns get some kind of strategic spell immunity on higher levels (I was playing on Expert)?  Screen shot below.