Mythruna won't have "heat seaking missile" monsters like some other games of note. If I have my way, all creatures (friendly or not) will have motivations beyond just "I appeared now I will kill the player".
There's an AI design methodology called Goal Orient Action Planning (GOAP).
http://web.media.mit.edu/~jorkin/goap.html is one launch point. The current AI design for Mythruna relies on this heavily with some additions to deal with the case where players are not around but the AI still needs to operate. For example, NPCs building a city. If the player is watching then you should see the buildings get built... but if you walk far away for some long period of time and come back then progress should have advanced as if you'd been standing there... but there was no reason for the game to bother doing the individual steps. "Player was away for 10 game days, buildings go up in 1.5 days so randomly place x number of buildings, etc."
Custom AI behaviors will be in the form of defining new GOAP actions which will have requisite conditions, results, etc. along with the additional stuff to know "average time" and how to interpolate mid-action, etc.. Building a creature AI is then a matter of giving it a catalog of actions that it can choose from and associating a hierarchy of goals.
For example, a wolfs base goals would be "eat when hungry", "sleep when tired", "hang with my pack". It would then have a set of actions to chose from (potentially sequences of actions it can chain together) to achieve those goals. And nearly every creature gets those exact same goals, it's just their actions that change.
For example, a deer might also have a "run when threatened goal" but its other goals would be the same. Its actions for finding food would be vastly different and its other priorities may be sorted differently.
I hope that clears things up and gives food for thought. AI is something I'll be diving into more deeply after physics is integrated because physics capabilities ultimately factor into everything else.