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Let me summarize:
Any hero can acquire a super ability. To do this, you need to:
a) Assign the required skills to 3/4 of the available slots (depending on the castle).
b) Max out three specific abilities for each skill.
It seems not too complicated, but the problem is that development usually doesn't go as we would like.
Here's an example. Let's say you're developing an elf. All the main skills are at the expert level, and at the next level-up, you are offered a choice: Dodge or Magic Resistance (for example)... and that's it, it's all over :(, whatever you choose, you can't follow the desired path. If you don't understand, take a look at the skill tree.
But there is a solution. There is a great program called HeroScanner http://www.maps4heroes.com/heroes5/download/rus/HeroScaner_13_Universal.rar, which reads information about the possible development of a hero (which, by the way, is already fully embedded when the map is loaded) and allows you to plan his development yourself; it's a very convenient tool. If something doesn't suit you, the entire tree is updated upon restarting.
In practice, I haven't developed a super ability, but in theory, it can be done no earlier than level 33. Do you really need it? In none of the Campaigns, my heroes reached such a level...
Где среди пампасов бегают бизоны, а над баобабами закаты словно кровь.