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Congratulations!
Antimagic is needed to protect against magical creatures in general, their magic, and to prevent the reflection of our spells – liches cannot be blinded (but it is possible to inflict amnesia).
It's strange that your approach worked: Madre has all the spells (I checked in the editor), wouldn't she allow herself to be blinded and remove the blindness? As far as I know from experience, the AI always tries to remove blindness. Even when the enemy hero has no healing, no spell removal, or no antimagic, they will definitely cast something (chain lightning, armageddon), which will remove the blindness.
Have you tried getting a Berserker? Maybe there is a way after all? Although, in general, this should have been taken care of after the first few months of the game (I'm mainly writing this for Xaart). Also, at the beginning, if it's important for the current map, I try to figure out what skills the main hero can acquire and in what order he should be developed. Most often, I am interested in earth magic, followed by fire magic and water magic: these skills are valuable on almost any map. And the rest depend on the situation. Tactics and ballistics are also very useful in battles.
Here's how I do it (there is a special utility, but I manage without it, doing everything manually): I save the game, use a cheat code to increase the hero's level, and record which skills appear and what I choose. When all 8 skills are obtained, if I like the combination, I take a screenshot and save it, then reload the game to continue. If the combination is unsuccessful, I load the save again, and this time, instead of something, I choose a different option. This way, I can find out in advance if I will "fail" with earth magic. In some cases, I have to assign another hero as the "parent" for this reason, and, of course, the sooner I do it, the better. I also sometimes find out what skills a secondary hero can acquire: most often, literacy is needed if you need to learn a valuable spell that the third hero has.