Creating "AI" Without Using Cards

Hi! Long-time game design aspirant, first-time poster.

I'm working on a co-operative game (also playable solo) with a fantasy adventuring theme. Original, I know! There are certainly some "catches" that set this game apart from the rest, but that's unimportant to this discussion.

What I need is an elegant way for the "monsters" to choose their targets when attacking the players.

Depending on how many "characters" a solo player is running, this may or may not matter during solo play (if you're the only player... the monsters always attack YOU!) but it matters a great deal during co-operative games in which multiple players are each running their own characters. Remember: there's no "game master" playing with you; the game is fully co-operative.

This game will NOT feature any deck of cards - just dice. For reasons I won't go into here, a "monster deck" is a non-option. The basic fighting mechanics revolve around characters using a pool of Action Dice to attack, move around, use special abilities, and so on. They can use whatever dice they do NOT spend on attacks, movement, and special abilities to defend themselves against the monsters when it's time for the monsters to act.

Monsters have static attack and defense values: you ROLL your attack against a monster's defense value, you ROLL your defense against a monster's attack value, and so on. That way, you're never rolling against yourself. What I'm having trouble with is determining which player (or players?) each monster attacks.

Because rolling dice is at the heart of the game, I don't want to end up with a system in which one character winds up rolling all (or even the vast majority) of the dice during the monster's turns. I can specify "attack conditions" (for example: goblins always attack the target with the smallest pool of action dice), but unless I include numerous different kinds of monsters, each with different attack conditions, in each in-game conflict, then I'll still end up with one or two players (i.e. the players whose characters meet those conditions) making ALL of the "defense" rolls. In addition, this method makes monster attacks VERY predictable, freeing those characters who know they will NOT be attacked from the decision of whether or not to save any dice for defense. This is a systemic side-effect that takes choice and tactical decision-making OUT of the game. Obviously, I'd prefer to avoid that!

Furthermore, every line of text that the players have to read or remember (e.g. "goblins always attack the character with the smallest pool of action dice") adds complexity to the game without necessarily adding depth or elegance to it.

I could have players roll a die to determine who gets attacked, but there are several problems with this as well. For one, that's a lot of rolling EVERY round, and - if you don't want to be the monster's target then it feels like you were "rolling against yourself" if you "win" the roll.

So... the question is: using only STANDARD (six-sided, non-custom) dice, token placement, and static values, how can I implement an elegant "AI" mechanic that allows monsters to choose targets (and preferably not-entirely-predictable ones) for their attacks without a lot of "if; then" logic or text-heavy "flowchart AI," all without ever forcing the players to roll against themselves? Can it be done (neatly)?

Your thoughts are appreciated; thanks in advance!

Daron Woodson
Abandoned Arts