And have the cats appear out of a mysterious abandoned mountain fortress?
The leader could carry The Sword of Old Men which has a lightning effect on it...
For some random events on the lower side of things:
-Volcano erruption- a mountain errupts like the volcano spell. The erruption itself could be preceded by tremors and/or a smoke effect if it is within say 4 squares of an improvement/ in a faction's teritory.
-landslide- a tile adjacent to a mountain tile has any structures or special terain types destroyed (wouldnt effect nodes or city cores)
-lightning storm- a massive storm spawns for x turns and a chance of forest fires, building fires or unit lightning strikes -use a light filter for effect (ex that dark twighlight contrast thing you sometimes see in real weather)
flooding- could come in a number of varieties, those affect improvements (require x number materials/gold to repair) that are near a coast or river. Major flooding could change a tile's elevation or type (ex swamp before dropping to below sea level)
Building setbacks- while a building is constructed or a unit is trained some mishap occurs that sets back its completion time. These could go the other direction too as an innovative solution to manufacturing or shortcuts.
Say my Name- an npc becomes unhappy with their name or title (either npc sov or unit) and declares to be called by another- they could also gain one against their will for specific actions or behavior accumulated. 'Emperor Fire Crusher Demands you to kneel!'- the sovereign formerly known as Magnar
Cultural works- these could include things like art, books building techniques, fashion, holidays, graffiti, superstitions, folk heroes and so on that affect the lives of the populace. The effects (if they have one- could be a further % chance) could range from permanent but small- probably more city/location specific to one time boons/costs. 'The clergy at a water shrine (belonging to any faction) have developed a secret advanced meditation technique for their sect developed from intense study and manipulation of their element.' this could either give a tiny bonus mana production from that shrine (a fraction of a point), give a one time bonus of prestige to the faction , or subtract some mana production for influence (a result of popularity among the people and the need to attend to them disrupting some of their studies).
Crime- their could be crimes or other things that pop up that are disruptive to the populace giving some kind of penalty if left undiagnosed. ex. a spate of murders in [Genertown] have effected its (growth/productivity). You could deal with the problem directly (lock the sov in the town for x turns while overseeing the case directly which may take longer to resolve than other ways) may lead to a combat situation and a penalty until it is done. You could increase security paying Y gildar to increase the towns militia size leading to a quicker resolution- the killer is more likely to be driven off then apprehended and may appear in another city in the world. Could post a bounty which would resolve it quickly but produce unrest and a chance of population lost due to 'falsely identified culprits'. Ignore it for now and hope it clears itself- no cost other than increasing unrest and lower growth productivity. Possible riots depending on how long it takes for the culprit to be driven off.- in this last case you would probably want the ability to change your strategy for the problem.
Any GalCiv style choices for your ruling would be cool (could have a hidden or visable resource accumulate based on your deeds to influence further events.