1. Some intelligent monsters attack only the weak;

• Wolves and bears will not attack an army of men; however, they will attack lone champions or sovereigns.
• Bandits will only attack if they outnumber the defenders - while 20 bandits may attack 10 defenders; however, they will not attack 100 defenders.

2. Dumb monsters attack anything they see;

• Rock Spiders of Intelligence 1 - attack anything

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. 

I really like the idea of bandits demanding gold for not attacking!

It could be quite cool if there would be even more of these events. When a dragon attacks you could have an option to avoid the battle and hide everyone. This would cause the dragon to kill a few citizens and destroy a building or something similar, and then venture off.

Or maybe a dragon attacking the city normally wouldn't cause the city to be completely destroyed but rather badly damaged, even if you lost the battle?

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.

What a monster does to the town should be a predetermined thing, with some randomness.

A spider might eat a few people with a chance of wrecking a building then leave

Bandits might drain your treasury, smash a building or two, and lower your population, then respawn somewhere in a few turns (perhaps with more bandits)

A dragon might eat a bunch of population, or wreck your town, or who knows

Demons might just take over your town, turn it into a demon town , then become a minor faction, or just destroy the town, replacing it with a bigger demon.

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. 

FYI, all they would need is a unittype check after the end of the battle. The function would resemble something like these lines:

function TownDefeated
switch attackingUnitType
case 'Spider' decreasePopulation destroyImprovement
case 'Bandit' decreasePopulation decreaseGildar
otherwise destroyTown

This suggestion isn't that code intensive, really. Don't know why you think it would be.

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.

Overall difficulty setting should be the main thing. I don't think we need a separate slider for aggression. That seems to be a needlessly complex addition that could be folded into the overall difficulty.

I really would love to see a variety of enemy behaviors, as many others have mentioned. Having bandits behave differently from wolves will help the world feel more alive, since the threats you face will have different motivations.

On a similar note, I really hope that different types of enemies will stop forming armies. I hated it when a bear would team up with bandits, or things like that. A group of spiders joining up to form a spider horde is cool, a bear, a wolf, and a bandit teaming up just seems weird. Now, if it was an evil druid or something, that would make sense and be cool.

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.

I love how in the Lord of the Rings there clearly has been a long buildup of tension.

So it would be cool if monsters, and especially wastelands, would slowly turn more aggressive based on events, how much you (or other players) harass/pressure them or just time passing. An event could be to get a mission you must complete to calm down a powerful wasteland (destroy the ring!). It could also be funny if you could on purpose harass a wasteland close to your enemy. With the risk that this backfires, and the wasteland turns against you.

Whatever is done, I hope there will not be a constant flux of irrelevant monsters. That just annoys the player. As much as possible, every battle fought should be meaningful in some way. It should not be common to get attacked surprisingly by a powerful monster. Especially in the early game surprise attacks by powerful monsters can decide the game without the player having a chance.

Most of the time the player should be informed (or he should be able to guess) that an attack is coming. There should be some way the player can know why the monsters decided to attack.

There could be this event: "The orcs are gathering in the mountains. Maybe we should send some patrols there?" -> The buildup of orcs start -> If the player does nothing, the orcs start to wander (and pillage) the farmlands -> If the player still does nothing, the orcs start to attack units outside cities. -> cities will be attacked. Clearing the mountains could be a rewarding, but challenging mission.

Similarly if there is a bandit camp, when you stay away of it, they stay away of you. When your borders start to get close to the camp, they will get a little aggressive (attacking units nearby), when the borders begin to pressure the camp, they will try to get rid of that pressure (more pressure, more chance of all-in attack against the city generating the pressure). Same could work with wastelands: if you give them little pressure, they will occasionally send scouts against you. When you pressure them more, they will start to fight back. If you attack them in force, they are likely to attack you back in force. Don't go harassing those dragons, they are easily annoyed!

2nd this

Right, like I said in the post right above yours.

Two more ideas about the wasteland harassment: some wastelands could be really picky about their borders - go in and they get angry. Other wastelands could be much more relaxed: passing through is OK as long as you don't visit certain sacred locations or do some other wasteland-specific harassing actions. (Don't cut down the trees of Fangorn...)

The second idea is again from The Lord of the Rings: a sovereign / champion class that specializes in controlling the monsters of the world. This could be direct recruiting, or special abilities allowing the character to raise aggressions in the monsters - and towards a certain faction. The Lord of the Rings reference would be Saruman. The ability could be magic or gold based.