I would prefer if their type or intelligence was referenced in their decision to attack.

So... very aggressive to aggressive only when chances of winning are good to somewhat passive. I'm sure that's a ton of extra work, but hey, you asked.

I would assume you'd want monster's difficulty level to be based on the world difficulty. Beginner/Easy level, they're pretty passive and you can just pick them off. Normal level, monsters will co-ordinate to defend their lands and launch small, obnoxious forays into your territory to destroy outposts. Hard/Flee-For-Your-Life Difficulty, the ravenous beasts will throw everything they have to take you out of the game. But maybe I'm misunderstanding the nature of the question. If you could only pick one of the above three, I'd suggest the normal level difficulty. That way, the monsters provide a presence

I also assume that we're talking about the strategic map, not the tactical one.

I read this as something different, and kind of cool. What if the level of aggression were based on the monsters in question? Say you've got a spider swarm. They're mindless, they'll just wander around and attack anything that moves. Then you've got wolves. They wander around and attack anything the pack thinks it can beat. Thieves and brigands eagerly attack trade caravans, unguarded cities, and heroes they think they can overwhelm, but are dreadfully fearful of sizable armies. Maybe you remember the Haunter - perhaps a group led by the Haunter would only attack groups with a magically potent character (or some other cool lore reason). So basic motivations would decide when and where each kind of monster category would attack.

Lies. 

MAKE A SLIDER! YES! (maybe you could change it in game too.) Different creatures acting in different ways too, ya I can see this is hard to figure out...

monster difficulty should be determined by its type.

Animals should be cautious, unless they like eating people.

Maybe some monsters like certain things?

Dragons and other very powerful intelligent monsters should attack anything whenever they think they could win. This includes cities.

Other aggressive monsters should attack whenever someone gets too close or if they wander close to a city, or if they are harassed in any way (ZOC).

Animals shouldn't attack unless the enemy is very, very weak or the enemy is too close to their lair or under special instrucions to attack for some reason.

Bandits should only attack weak targets.

Basically, I agree with the argument of it should change based on unit type.

Take into account that no monster is going to just randomly rampage without a reason, and that if monsters are little more than beatsticks they become faceless and pointless in the grand scheme of things.

Personally, I'd prefer a scale - between more docile (monsters individually avoid cities and push away from them, perhaps forming small tribal communities or eventual huge armies) and incredibly violent (monsters see anything that isn't them and attacks) as the two extremes.

More to the point, are monsters just there to cause problems? Or can they be used in alternate ways?

So long as I don't get the occassional situation (as happened a couple of time in elemental) when i'd be attacked by armies of monsters that i could not by that point, have raised forces to defeat, I will not be too annoyed.

The problem is not IMHO in the AI in this instance, but the all-or-nothing nature of assaults. You either get attacked and defeated in your main city (game over in the early game) or pretty much nothing happens. If bandits would demand gold in return for not attacking, that could allow them to be much more aggressive.

But more than anything, the game really needs a siege mechanic like in the Total War games. That way, less than awesome enemy armies could attack cities and do meaningful damage (deprive income, steadily deplete the defenders over time) without attacking outright and spelling game over. If armies were required to besiege for a few turns whilst building assault equipment, it would also make it much more difficult for human players to rush the AI and move down the road to from their town to the AI's and capture it, all in the space of two turns. You'd get more interesting situations like armies from other cities coming to one city's relief. As I say, the Total War games basically do this perfectly.

This really belongs in the wishlist, but oh well. 

There should be two stats to determine a creature's attack probability:

1. Aggressiveness. This could be called rage or bloodthirst as well. This would be the distinction between a defensive creature merely looking to defend its territory and the kind that exist merely to rid the world of humanity. 

2. Intelligence. This would determine how likely the enemy is to consider your city or army's power rating before engaging. Creatures with higher intelligence would group up until they had a comparable force or simply run away if you are that powerful in the area. Dumb attackers would base their attacks purely on aggression and smart but aggressive creatures would weigh their chances of success before attacking, but probably ultimately attack sooner rather than later. 

So, if for some reason you started this thread to determine how to determine aggression, there you go. If you already have a system, it would be nice to be able to separate monster aggression from difficulty level. Or at least give us a choice in the XML so I can make my own difficulty levels. 

Yeah, bears and bandits leaving whole towns instant smoking ruins tends to spoil immersion in WoM... so if there's a way to get certain creatures in FE to attack more without necessarily resulting in the catastrophic and instant death of the whole town, that would be excellent (as well as helping people not to feel they are getting attacked "too much" ).

Best regards,
Steven.

I don't see any way they could add this without a crapload of new code. I find it realistic that creatures mostly attack your city while defending the land they own, that you have tried to take. So they kill all your people and generally turn your fledgling city into ruins. The solution I have wanted for awhile now is for the peasants of the town to be able to lightly defend it based on the population. This would be much easier to implement. 

I agree with LNQ on this. It's not difficult to have static behavior added (or supplemented) in a way he outlined. What is difficult is having good AI behavior that is not predictably deterministic.

I did think of one problem, combined monster armies.

Then again if a spider meets a bandit, they should fight it out, not join together.

There should be different monster 'factions' if that is possible.