Inferno tactics.

Is Adela a good hero??? hahaha

Heroes whose specialty is spellcasting (levels 1-2, buffs, etc.) are just as bad as their specialty! )))
Therefore, if I play as Elementals, I take warriors, because mages have a crappy specialty!!! Magic Arrow, etc.... Would I really use Magic Arrow when I have Chain Lightning or Explosion???

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If I'm not mistaken, the Demons also have a hero with a special armor skill, and he's pretty good...

It's permissible to laugh at your own mistakes - that's more polite.))
But I insist - Adela is an excellent hero because of the Diplomacy skill from the very beginning... having Diplomacy at expert level and some money (which is quite likely for the Castle, given the lack of large expenses on the initial army for clearing the territory - upgrade archers and halberdiers, and that's it!!!!)
you can, with a high degree of probability, quickly recruit units of levels 1 and 2, at least - and with this army you can clear a lot! at least by putting units from other cities under attack. And the Blessing that Adela has will allow archers to deal significant damage with their double shot.
Arandor, are you seriously saying that Diplomacy is an unnecessary skill???
hahahaha!!!!!

Added 5 minutes ago

Are Spawn of Evil pointless? I don't think so. Extra defense and attack never hurt.
Intelligence is not needed? You can make an excellent mage with a huge amount of mana from Aiden!
Learning may not be that important.
Magic, especially with a specialization, greatly increases magic damage. Zydar turns out to be a good mage.
Chain Lightning may be funny, but it's given at the beginning of the game, and the hero doesn't have any extra skills.

Spawn of Evil - a small number of hit points won't make them good fighters, despite the increased attack and defense.
Almost all mages are offered the Intelligence skill, and Knowledge is also developed. There is a chance to make a mage with a monstrous amount of mana at the expense of everything else.
Learning - you put it mildly.))))
Magic doesn't "greatly" increase magic damage. only by 15%. if the Explosion spell, with expert level in Earth magic, takes, for example, 1500 HP, then an increase of 225 HP won't play a significant role in order to take up a slot... moreover, Explosion is not immediate and not always... on weaker spells, this is generally imperceptible...
Chain Lightning - I completely agree with you... it's really funny...)
But the absence of unnecessary skills is also good... for Inferno.))