I killed the Ents without losses in both creatures and mana.
Earth Elementals without losses but with zero mana.
Your hero skill development path is strange, shoot-nick, but that's your business.
Who needs mana regeneration when you have a Soul Eater — full mana after every battle? And why did my Gilraen leave the city only on the 21st day??? That's the only downside of your description; does he really come out when you approach the Castle??? Oh, this great I (this is not a typo, specifically I, and not AI; that's how we usually refer to the AI currently present in Heroes. Just "Artificial." I really hope that someday it actually becomes a real AI)