It's strange, I can even put 6 (of course, specifically for research purposes), or does it mean that only 3 auras work? Where did you get this information? And by the way, which cell of the unicorn spreads the aura? The head, the rear, or both?

I think you can put 6. I just took 3 for the calculation for some reason :) I can't say for sure which specific cell works because I haven't tested it. I used to think that the aura is spread by the *rear*, because in the game, in the tavern, there was once a rumor: "If you want to protect yourself from magic, stand BEHIND the unicorn." That's why I thought that only 3 can be used and they must be behind. I need to test it sometime. It's also interesting whether the aura will work if the unicorn is cloned :D

And right away, a related question - 40% resistance - is it a 40% chance to completely reflect any enemy magic, or for damage magic, does it always reduce the damage by 40% (it seems so, but I don't remember for sure)?

It's exactly the chance to reflect any magic. The chance to reduce damage only applies to golems. Although in Warlords, they wanted to change the effect of the skill to the "golem" principle, but the idea didn't seem to make it into the final game.