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I think that if anyone can obtain the source code or make changes to the game itself using an alternative method, it would be the guys from here:
http://heroescommunity.com/forumdisplay.php3?FID=18
They will be able to obtain it, as some forum members have contacts with insiders at Ubi, but whether they will share this information with the community – personally, I have very strong doubts!
Regarding alternative methods, you need to look for specialists on forums specializing in reverse engineering!
For example, here:
https://tuts4you.com
https://www.reddit.com
https://reverseengineering.stackexchange.com
С уважением, Psatkha (Псатха) 
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Неудачное планирование ведёт к неудаче ...
NCF - мод, добавляющий дополнительных существ в HeroesV 3.1

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Неудачное планирование ведёт к неудаче ...
NCF - мод, добавляющий дополнительных существ в HeroesV 3.1