Posts from New objects (in towns, etc.).

1) Worker-investment guild.
Provides interest-free loans by taking units. These units work to pay off the interest. To return the units, you need to repay the loan.
There is also a possibility that the opponent will buy the units, which is especially dangerous considering that they are pledged for less than their full value.

2) Secret underground passage.
Allows you to leave the battlefield with your army, and also to "disappear" completely within a day. That is, the hero and army go into service.

3) Old mine.
In case of an attack, it allows the hero to hide in the mine, and then cause a cave-in in the section of the mine where the battle takes place. This results in both heroes and their armies being buried in the mine.

4) Master Trojan builder.
Builds Trojan horses. When launched before an attack on a city, the Trojan horse starts the siege with the gates open.

5) Customs.
Takes a percentage of the army's value for passage.

Let's say that if both armies are trapped in a mine after a collapse, they will remain there until someone digs them out. Each turn, a portion of the army will die from hunger (or something else), so it's important to dig them out before it's too late. When digging them out, there could be two scenarios:
1. An army is dug out (one of the two) by an ally/army of the same color. Both armies then fight the enemy army in turn.
2. The army is "neutral." Whoever digs them out fights both armies, and the winner is chosen from the mine.

Maybe we can find a simpler solution?

The third option: one of the armies can try to break out on its own. This requires resource expenditure and a significant time investment.