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Here's the answer, a couple of years late!
Of course, instead of going for the crown, we complete the mission to gather troops.
Here, the question is whether the map unlock code and loading the save file are considered cheating, especially if the code is written on a signpost in mission 5.
So, in the mission to gather troops, we rush directly to the Sorcerer's Castle, capturing a small number of stone, sulfur, and mine tiles along the way. Then, we rebuild it, clearing the path for the second heroes to gather resources, who can be recruited there. If we're lucky and some dragons join our party on the map, we'll end up with 36 combat points by the end of the mission, as I did. If not, we'll have around 20 after capturing the last castle, plus the rest of the army – which is also needed.
In the final mission, we give Roland 15 dragons, which is enough to defeat any enemy without losses. We then divide the rest of the army between two heroes and rush in all directions to capture everything. In the direction of the Necropolis, my hero failed, but the others quickly arrived from the Sorcerer and Barbarian factions.
The Barbarian Castle at the top was captured by the already built Barbarian army. After capturing all the castles, starting with the Sorcerer's, we gather the best troops, led by dragons, in a couple of weeks and easily defeat Archibald, who had far fewer dragons than I did. There was no Armageddon, and most of the enemy troops were controlled.
In general, we use a gameplay strategy similar to the "genocide" plan in The Curse of the Serpent King.
Quite a successful move is to capture a castle right under the nose of a strong enemy hero and set up nearby. The enemy takes the castle back and leaves part of their army in it, which helps in battle, if, of course, the enemy doesn't decide that they are too weak and doesn't stay in the castle...