It's starting to feel more like an RPG...
I also remember an idea about sabotaging mines and putting them out of commission.
It's still okay for a single-player game.
The special ability will be passive for the hero when attacked by an enemy. Also, it shouldn't be possible to disable the garrison to take control of the army, as the game already has a different purpose for it. And besides, there's a lot of situation tracking involved.
It would be better to create a spiritual connection with the hero's object. For example, an enemy attacks a mine, but before capturing it, they encounter our hero with the special ability.
The number of troops will depend on the hero's level. The army will be virtual until the attack on the object. Regarding events, you can create a separate function that will handle events specifically for the mod and for the map. Making a "spiritual connection" would be imbalanced: it would involve interaction between heroes who may be in different parts of the map.
Added after 42 seconds
I remember that in an old version of NHF, there was a hero who specialized in bone creatures and populated mines with them. We had to remove him.
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