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Oh my god, I'm scared of you))))))))))))))) Do you also use Chaos for the Barbarians?))))))
Well, in any case, Light magic will be better because it is much less tied to witchcraft than Dark magic. Witchcraft only affects the duration of the effect, and the number of units resurrected during resurrection, while Dark magic is more strongly tied to witchcraft, and since we have problems with it, then...
Although, I can also provide support with Light magic and units that are spellcasters (monks, angels), but only the hero can cast Dark magic, so the answer is not so straightforward, but I still prefer Light magic.