I recall chatting with a fellow GM who was running D&D 3.5. “My magic-using PCs keep dying like flies,” he was musing. “It could be because I always target them first with all available ranged attacks”. What followed was a discussion where I suggested maybe he should have tipped off his players to cast Entropic Shield, Mage Armor and so on before wading into a combat. Yet during the course of the conversation, a thought nagged at me at the back of mind. Should NPCs in combats act as though they belong to some hive mind?
Should the GM Meta-game his NPCs in Combat?
The question can be boiled down to one thing – should NPCs be privy to “meta-game knowledge’ and use that to their advantage? For example, in CRPG such as Dragon Age and Final Fantasy, we all know to go for the healer first. Or the crowd control specialist, because they are easy to kill and a big nuisance if they are left alive. Yet the attacking goblins (or pack of wolves) does not know the characters’ spells. Perhaps they couldn’t even know who is the mage. Is it fair for the GM to target those valuable members of the party right off the bat?
Likewise, should non-intelligent or untrained group of mobs fight with the precision of a master tactican? Usually, the good tactics are go for the weakest link, disable the strongest attacker as soon as possible, focus fire on one target till it drops and try to obtain first strike. In fact, the last one is so prevailing that I have been in a game that the NPCs do not advance, just standing there firing their ranged weapons till the PCs got bored and charge.
Tactically sound all these things might be, it is realistic that all NPCs across the entire landscape use the same tactics, just because they are controlled by the same GM? Would a bunch of town militia fight as effectively as trained adventurers?
Why AI for Mobs
There are a few reasons to come up with some guidelines for each group of NPCs to run in combat. The two important ones to me are:
- So that combat can be fun and exciting
- The GM does not overpower the PCs too easily
Realism could be a far third.
Let’s turn the attention to reason #1. Let consider the case if you play as a ruthlessly efficient GM, and in the first or second round of combat you manage to down the mage or the cleric. So what should he do for the remainder of the combat? And if by some stroke of luck, your favored target survives, your horde are effectively ignoring the rest of the party. Do they feel any risk in combat?
The second reason is that most modules give NPCs who are stronger or the same level as the PCs, and usually the GM already have an over-powering odds. If the GM plays ruthlessly, the players may be overwhelmed too quickly and become frustrated. Also, a player only has one PC, but the GM has numerous NPCs to throw at them. There is always chance for the GM to steamroll the players later on. If not this session, then the next.
Do take note that I am not advocating making every fight a walk-over. Far from that be. Bored players aren’t having fun at all. This is an important, delicate point in game design and balance. Too easy, and the players are bored. Too hard, and it is frustrating. Case in point, have you ever tried to play against a Chess AI at Grandmaster level and got trashed within 10 moves? (Pardon me if you are a Chess Grandmaster or frequently pound the AI into the dirt, it’s just an illustration).
The idea here is to avoid one-shot kill. In Diablo 2, there are many one-shot bosses and creepers and most people hate them. The Fire Enchanted and Lightning Enchanted unique champions come to mind. And Corpse Explosion in Hell difficulty. One-shot kills are not fun. You have no chance to survive…So the idea is while you can trample over the players and take down one party member by round 1 or 2, maybe you should reconsider so everyone could have some fun.
Guidelines for NPCs
Here are some guidelines I have devised on my own. Unlike a scripted AI, a GM can be flexible. A lot of the ideas here follow “movie logic”, not real life logic. So, if I am a monster, I would:
- Attack closest enemy
- Attack the closet enemy threatening me. No matter how enticing another target may be, unless instructed, the dude in spiky armor with a large knife in his blade who is just next to me is more threatening than anything else
- If I am otherwise unengaged, attack any ranged attacker who is targeting my ally.
- If unoccupied, I will help a surrounded friend.
- Last touch: the one who hurt me last or tried to attack me most recently gets my attention
- Field of view: I would only consider targets which I can see, follow by those I can hear.
- If a foe is otherwise distracted, and no one is attacking him, and I am not preoccupied, I will attack him
- Seize advantage: if an adjacent foe is hurt, and I am unoccupied, he will be my target.
- If I have been trained to fight with my partner, I will stick with him.
- Rule of three: If three allies of mine are attacking a target, I would move on to someone else because I would just get in the way.
A lot of these guidelines consider the NPC from the his viewpoint. Am I being attacked? If so, my attacker is my priority. It is not easy trying to aim a bow at someone while dodging an axeman hell-bent on taking your head off. Likewise, enemy rogues may like to surprise mages who are casting spells and they are soft, juicy targets – but only if they are not otherwise being threaten.
An alternative to having AI for your mobs is to model crowd control and taunting rules in combat. D&D 4E combat allows the player to influence NPCs’ behaviour with the use of marks, and to protect their allies with shifting abilities. Hence, the responsibilities of keeping monsters away from their weaker friends rest in the hand of the players.
There are many other ways to use rules but I believe giving NPC mobs “movie-logic” behaviour is a rules light way to go, and I do feel that the concept of ‘aggro’ can be artificial at times. In the heat of battle, it is already hard stay alive, much less calculate threat and re-prioritize targets. Of course, if the NPC force has a leader or a commander, then it would be a different story all together.
Commander AI and What are the Crunch?
Of course, I have not touched on the effect and presence of leaders in so far. I would look into that next time. One last thing – these “AI” are not rules, just some possible behaviors for NPC. Hence there no rules for taunts, distractions and so on.
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December 28th, 2009 at 5:40 am
I like these rules. Combat tactics is a personal weakness of mine – my enemies usually surround the closest thing to them, then just flank and attack anyone within movement distance of them for the rest of combat. But thinking back, two of the most exciting combats have been when the enemies did something different – for example, when our paladin decided to try and convert some goblins mid-combat. Guess who was unconscious by the end of the next round?
December 29th, 2009 at 1:42 am
Nice post.
Also, if the NPC’s are particularly brave and/or well-trained, make some perception-tests if/when spells start to get thrown around. A well-trained solider or a seasoned adventurer/villain should be able to recognize who’s casting healing spells, and -might- re-prioritize targets accordingly. On the other hand, not many intelligent creatures would risk several attacks of opportunity in order to take a shot at the mage.
This can up the challenge for the PCs, as they need to work in order to protect the squishies.
December 29th, 2009 at 1:47 am
I fully agree with what’s been written. Here’s a good place for GMs to roleplay too: have enemies act as one would expect them to. Goblins should be rather stupid and cowardly but overwhelm you through number and dirty tricks. Also following movie-logic, you tend to have characters of the same level or class fighting against each other, rather than have the big fighter against a weak caster.
December 29th, 2009 at 3:27 am
As always, the big question is ‘What kind of game do your players want to play?’
If your players want a detailed tactical game, then by all means, meta-game and have cowardly goblins sacrifice themselves to charge the mages. If they want a ‘realistic’ simulation, then try and role-play each NPC’s motivations.
Also if there is a leader commanding the NPC’s, make sure to allow the PC’s to try and perceive who’s giving the orders, and to try and neutralize them. Include some contingencies for what the NPC’s do if the leader is slain.
December 29th, 2009 at 12:32 pm
Good point on the type of game.
For me, when all the mobs demonstrate the same tactical behavior throughout, it feels to me that it is the players vs. GM. While giving mobs behavior that they naturally would have is a more narrative approach.
Another good point for the morale/courage aspect. In fact, ignoring an attacker to go help out an ally may require a morale/courage/willpower test, to see if you even have the presence of mind to do it. The PCs may have to roll this for a grim and gritty setting.
Sometimes I just let chance takes over. I told the players recently, “I’ll roll a d6. On a 1 to 3, it will attack the fighter; on a 4 to 6, it will attack the rogue”. This is after both characters have badly hurt the mob in question.