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1) Pure Rage - Orcs - a good bonus, but not critical; you can do without it!
2) Urgash's Call - Demons - difficult to obtain and not the best development path!
3) Relentless Force - Humans - an absolutely unnecessary skill!
4) Scream of Horror - Necromancers - very good, but not always needed, for example, against Necromancers))) or well-equipped and armored Haven units; it also requires spending the hero's turn!
5) True Luck - Elves - super, but developing secondary skills can have a negative impact against Necromancers and Fortress!
6) Absolute Defense - Dwarves - basically a foolproof option, Chaos for shorter games, Summoning for longer games! A good option!
7) Fury of the Elements - Dark Elves - a good chain, but in longer games, it requires a lot of spellcasting!
8) Arcane Knowledge - Wizards - a super choice, it diversifies the wizard's build!
I believe the best is for Wizards!
Excellent - Dark Elves, Dwarves!
Good - Elves, Necromancers, Stronghold, Inferno!
Unnecessary - Humans!