Which files need to be modified to add it as an NCF?
You need to create a lot of files; here are some of the simplest examples: Malachite Gargoyle and Ulem
You will need the following software for this:
1) File manager Total Commander
2) Any archiver capable of compressing in native ZIP format; I recommend the free 7-Zip
3) Texture and other graphics file viewer; I recommend the free XnView
4) Text editor like Notepad; I recommend the free AkelPad
*
It is best to edit textures using Adobe Photoshop (version 7.0 and higher) with the DDS plugin installed, but you can also use any other similar program!

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