Awakening of Evil

I don't understand what you mean by "sacrificing for your own growth"? Are you talking about the sacrificial altar? But for some reason, I had growth at the beginning, and then it stopped. Maybe you need to sacrifice a large number at once?
And most importantly, how do you get an additional hero? How much reputation do you need to gain? And from whom and where exactly do you get it? I'm tired of replaying.

The Dark Elves seem to have 2 camps with buildings. Plus, not far from the exit to the surface, in one of the camps, there is a building that adds 5% to your army each week. In the long run, it multiplies the army several times due to compound interest.

Additional heroes are given in the cities of Humans and Orcs. As soon as you gain 25 reputation with the Orcs, a message will appear saying that a certain hero, who is standing near the border of the Castle, wants to give you a quest. You approach him, take the quest, complete it - and you get this hero and his Castle at your disposal. At 25, 50, and 75 reputation with the Orcs, it works like this; I don't remember for the Humans, but the principle is similar. Many quests overlap with each other. It's better not to rush to kill anyone until you complete the quest. For example, it's better not to rush to complete the quest from the Elves and kill the mine guards before completing the Orcs' related quest. The mines will come under the player's control as the reputation with the factions grows.

Added 4 minutes ago
And it's not necessary to complete every quest and gain 100 reputation. 75 reputation with Humans or Orcs is enough to complete the game.

Added 1 minute ago
Before taking quests from the main heroes, it's better to make saves