Immune to magic that affects the mind. Auto-translated

Hello, reader! I've noticed something for a while now: some heroes have immunity to blindness, even when they don't have the Amulet of Inner Vision. I've encountered this many times, but it remains a mystery to me – why does this immunity appear? This question has been bothering me for a long time, but now I've found that heroes also have immunity to forgetfulness, berserk, and hypnosis, i.e., everything that affects the mind, just like Titans. So, what is the cause of this immunity? P.S. If anyone is interested, I have save files that clearly demonstrate this.

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Oh! I came to write that the question is no longer relevant, but I already received an answer. Thank you!