Editing Horn of the Abyss (Documentation) (section)

====Choosing the fighting heroes====

* Players are selected first: if no one is standing in a combat place, the attacker will be the first player by the turn order and the defender is the next one (excluding the first player’s allies). That considered, if there are heroes in some combat places, the defending player is chosen among the owners of these heroes.
* If it is not possible to select players in this way (all combat places are occupied by the allies of the first player in the turn order), the defender will be the first player in the turn order, and the attacker, the next player. If there is only one player on the map, he wins immediately.
* For the battle, the strongest hero for the attacking player is chosen (by the army value, taking into account the hero’s attack and defence stats). If a player has no heroes on the map, the strongest one among those in towns will be chosen.
* Fot the defending player, the strongest hero among those standing in combat places will be chosen. If there are no heroes in combat places, then the hero will be chosen the same way as for the attacker.
* If a player has no heroes, he automatically loses (mutual loss is possible if no one has heroes).