Curse of the Tribbles (Strategic spell) - Summon a single 'unit' of Tribbles. Tribbles roam the country and will multiply every so often turns (by spawning a new 'unit of' Tribbles), and in doing so will turn fertile land into barren grounds. Kill them fast or live in a barren world.
It would be fun that if it would go on unchecked for a long period the land would swarm with them (and be utterly barren), and for every step you take you have to carve a path through them first. So individually they should be rather weak, because theirs is the power of attrition and multitude.
"Look, cute cuddly furry creatures. How can they possibly be harmful to anyone or anything? They are so weak and little."
Shard of Consumption (Strategic spell) - The shard on which it is cast will slowly destroy the lands around it, damage all units within a given range, generate more magic (depending on the damage done to the landscape and units), but it will slowly destroy itself.
"Sure, you can have more magic now. For the small price of the destruction of the lands, some life force of the unworthy or the careless, and the inevitable obliteration of the shard. But hey, that is a worry for later, if you don't survive now all that is worthless when you are dead."
Blessing of mindless relaxation (strategic spell) - Turn an area into fertile terrain where units generate health faster, but accumulated experience points will actually decrease. If the terrain is within city limits the production in said city is diminished, but unrest is lowered. Any combat on this terrain will be influenced: less chance to hit / block / etc, and will give less experience gain - in other words all the combatants will fight like incompetent morons.
"Come and put your feet up, relax and rest. No need to worry about anything. Here, have a toad from the vale of the happy people, if you hold him in your hand for a while you will start to feel really good. And then i am not even talking about how happy and relaxed you will feel if you lick him. It will be groovy. Eh man, you know what i mean?"