Yes, no problem.
1) Where should I add it? Only to a specific map or for all maps with the mod?
I will have to modify each map where he might appear.
2) The easiest way is to download and analyze this mod. It will be more difficult to analyze NHF. This mod already modifies all standard maps.
3) Guardian Angel can be added to any hero, but it will only work if the hero has at least basic Light skills.
Yesterday evening, I spent the whole time analyzing NHF, and now I'm stuck. Can heroes be added through H5u or is it necessary to use binaries?
Here, existing heroes are unlocked, but I want to add a new one, with its own image, story, and skill... And also, the heroes from NHF appear on all maps, including downloaded ones.