[Endoperez]

Dominions II had a theme in which Pangaea started the game with Carrion Woods as a dominion effect. They had Nature/Death mages and level 0 national spells for summoning the Carrion lords and ladies and critters that now have to be researched. I don't remember how good it was considered, but I doubt level 0 Carrion Woods is as big of a problem as you think. It kills off population, reducing your income and your capability to recruit normal troops or mages.