Hello Uriel Septim X and AlexAnt! In MMH5.5, there are two types of stacks: mixed creatures and single-creature stacks. - Mixed creatures: These are set with the mood "Hostile" and Courage "Flee_join". This means the mood specifies the certainty to attack or do something else. In this case, it means they will always fight, disregarding hero army size and diplomacy bonuses. - Single creatures: These are set to the mood "WILD" and courage "FLEE_JOIN". I am not completely sure what WILD means (I could not find it in the documentation), but from practical testing, I believe it is half friendly/half hostile, so it is susceptible to diplomacy and army size bonuses and CAN be joined. This is also valid for monster of the week creatures that appear on the map. One can use Mapmixer to make all creatures wild or friendly (including the mixed creature stacks), so the players can have a chance to join them.