AI mechanics

Kingdom Death: Monster looks to have a good AI system for monsters, at least judging by preview materials.

I wrote this little article on AI, maybe worth a read. They are might give you a little perspective on AI.

For an AI to be good it must do the following things:

-appear to react to the player(s)
-Act logically, but not 100% predictably
-Give the players a challenge

The two most common AI structures in board games are seeded random and condition/priority because they required little complex math and are easy to follow by hand.

The condition/priority is the easier of the two to understand. The idea is basically that of a flow chart. The game asks the player questions about the game guiding them until the player receives the action the AI is to take.
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This may require tracking extra details that a human is aware of that is not necessary tracked already in the game. For Example in Risk the game does not track which players attack which, however if one player keeps attacking the AI, that might be a factor in their decision. Or even factors like what turn in the game it is.

The first step to making a table like that is to notice how you make choices in a game. In a sense you are to come up with an ordered list of priorities.

The first things to worry about is victory/defeat concerns, time-limited concerns, time-limited opportunities general play.

Start with a first concern and ask yourself how should the AI react to this. Do not be afraid to make a sub-priority list and break it into further reactions.

The two most important things to remember about this type a AI is the flow chart must have some unpredictability even rolling dice for actions at time (but not too much).

The AI also needs to react to its enemies, if a player offers the AI a trade agreement it should not simple reject it but instead offer a counter offer.
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The other form of AI I've commonly seen in board games I call seeded random. While the condition/priority was good at having reactions to players. The seeded random generally plays more of a grand strategy and generally is easier to run.

Seeded random is most commonly utilized with cards. A card is flipped and used for a particular action. However, if it were just that simple the game would have no reactivity. Sometimes a new card is flipped every turn and other times the current card is continuously used until it meets a condition telling players to draw a new card.

The reactivity of this seeded random comes in the form of what most board gamers would describe deck building. The idea is players generally continue using the same types of strategies so it 'learns' how to counter that strategy.

For example the game is rock paper scissors. The player throws scissors and the AI picked paper. Since the paper lost the paper card would be removed from the deck and replaced with the superior rock selection. Of course in rock paper scissors the player will pick up on this and quickly switch strategies, so the system works best when it is either hard to switch strategies or if the player does not know its happing. The AI can even be allowed to adapted over multiple games.

The first step to designing this kind of AI is too pick all the pick all the realistic paths to winning. If your game only has one realistic path to winning you either have a balance issue that should be corrected first or it is not good for your particular game.

Then determine the actions commonly associated with a particular strategy and make action cards in sets.

Then determine how players would counter each strategy. These can be in the form of specific actions or in the form of a count strategy.

Then for each action determine a conditions when you could not want the AI to do that action. As sometimes when an action is drawn you might want to draw a replacement as ever action is not appropriate all the time.

Finally add rules for exchange card add cards or removing cards from the deck based on the strategies and counter strategies you came up with earlier.

This type of AI is difficult to design and only useful in game that favor many play styles but if it works if is really cool.
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Unlike humans, if your AI is not good enough it is okay to have them cheat a little. Usually, it is better to make changes to the AI instead of having them cheat, but if the AI is getting too convoluted or you just can't think of improvements make it cheat only a little.

On a minor note I have not done much with board AI design, but I have worked instead with computer AI and these are based off of that.

These AI can of course be combined and an endless version of variants can be thought of.