Angels, unicorns, elementals, constructs, etc. still cannot be raised as undead, in accordance with the canon... The remaining units can be transformed into undead, as before.
The main goal of the mod is to eliminate the headache and guesswork of the type: "Which units will I be able to raise by killing paladins? Probably Death Knights? - No, only vampires...". There is, of course, a mod that clearly demonstrates the original undead table in the game, but it is not always convenient to use. And why? Why, after killing a creature that is an order of magnitude stronger, and suffering significant losses, do you end up with the ability to raise a creature that is often much lower level? As a result, the army becomes too disproportionate. As a result, the undead begin to overwhelm creatures of a low level, especially this trend is observed in the early stages of the game.
Now, after killing a creature, you can determine, by analogy, which specific unit from the Necropolis faction will be possible to raise.
Understood!

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