Basically, while playing as Inferno (supposedly the weakest faction:)), I was beating Necropolis (supposedly the strongest faction:)), both in battles at all difficulty levels and in duels with different combinations: strength against magic, magic against strength. I also played Necropolis in duels and won. But it was much harder with Necropolis; not many troops remained in the army, while at the end of the duel, more than half of Inferno's army remained alive, and Inferno fought great, ALL units.
My favorite tactic in duels: first, I destroyed the enemy's 7th-level creatures with my own 7th-level creatures and the Ice Block spell:), and the rest fell afterward. I often used "Mass Slow." From my troops, I resurrected 7th-level creatures first (when playing as Necropolis), then medium ones, and those with the fewest remaining.

I don't understand why the Weaver loses 1 turn to transform from human form to spider form. And what does the human or spider form change? How much do the combat characteristics change?

The funniest thing is that I couldn't play Necropolis against Necropolis, neither magic against strength nor strength against magic; maybe I was just too tired:), or I simply didn't study the Necropolis army and their abilities well enough. I will study them!:) But when Necropolis fights against Necropolis, it's something else; they fight masterfully. First, they destroy the medium units with the whole group, and then they surround the Weavers with the whole group, and the Weavers quickly disappear. Respect for their military skill.

And one more thing. Wouldn't someone tell me how they fight in duels? Who is better, who is worse. It would be interesting to read. Otherwise, they just stick to the cliché "Necropolis is cool, Inferno is weak." That's not interesting. IMHO.:)