First up is stopping the trickle of wraiths before they get serious. I found a crack in Tlaloc's defenses; while he parked 9(!) wraiths in his capital and in another forward city, and I had to keep sniping single wraiths while they weren't stacked with anything, I was able to take a city defended by regular units with my rising berserker numbers. From there, I skipped the wraith city and went looking for other targets, slowly claiming more and more cities. A Chaos Rift went up over Tlaloc's capital to start chipping away at wraith hp, a couple fire storms to hopefully help, and finally it was time to go for the kill. A pair of small attacks used up his stored mana while allowing a flame strike at the defenders, then the real assault was able to pick apart the badly weakened undead flyers. Conquering this island of decently developed High Men and Halflings solved my food, gold, and future infrastructure problems in one fell swoop.
During this war, I learned that I misunderstood how Wrack works: It doesn't target every unit for 1 damage, it targets every figure in every unit! Berserkers are durable and resistant enough to cope, but Halflings really suffer with their high figure count. This spell is a lot stronger than I thought even with that +1 to enemy attempts to resist. Black Prayer makes it even worse, if you can use both.
A couple paladins showed their faces during the Tlaloc war, and I'd like to report that while Wraiths wreck Berserkers and Paladins (probably) wreck Wraiths, Berserkers wreck Paladins pretty well. It might go the other way if the Paladins got to use their First Strike instead of Berserkers using their Throwing, but AI dumb.
Horus is an angry guy, being as at war with everyone as I am. Since he's sharing a continent with Oberic, leaving Freya all alone on Myrror, I decide nature girl needs to be my next target. Also, the constant Behemoth production is scary. Happily for my current situation, her land mass is also pretty poor in terrain (lots of deserts and mountains), and the AI is too dumb to use all that nature magic to fix it. I won't be able to fix it either, but at least I'll be able to fight. She has spread Draconian and Dwarf cities out pretty well, so there's a fair bit of fighting to do. She's also had time to amass a pretty good spell skill and Hard difficulty is keeping her supplied with mana, so even skirmishes with single weak units tend to be bloody. Cracks Call has drastically reduced the War Troll count, and a combination of Cracks Call and Ice Bolts have made the guy who runs my unit payroll happy, removing more than a few berserkers and slingers.
I've found that a group of Berserkers actually do a pretty good job against Behemoths, in a many vs one scenario. Figure 3 or 4 zerks can kill a behemoth as long as the zerks can all gang up on it? Even Iron Skin didn't seriously change the math. Much like Wraiths though, I think a stack of behemoths will be untenable for getting any kills before the berserkers are wiped out. Unfortunately for me, Freya has chosen to guard her capital with 5 behemoths, 3 basilisks, and her version of the champion Deth Stryke. I'll just...come back later. This might be one of the best guarded AI capitals I've ever seen, and I do not have a plan for this.
Efreet is my strongest available summon. Speaking of which, I need to call up a few and see how they perform. Berserkers, Slingers, and War Trolls have been slow pushing for me, and I have enough cities producing that attrition is no longer a concern. I still dread the blood bath that would be necessary to win against such a beefy horde. I may need to just take the rest of her empire and then see if she can still pay all that maintenance. I fear the answer might be "yes", and these aren't Death creatures so Chaos Rift attrition isn't going to be a thing before the heat death of the universe.