Which race would you add to Heroes?

Ha, a Barbarian city? They are nomads; they can't have cities. Come back down to earth—Heroes 5 is not that kind of children's universe where there is a division between good and bad. Here, everyone is bad. This universe is more thought-out, and if the Nival developers use old units, it's only for game recognition. That's why you go with High Elves.
P.S. Goblinoids, Barbarians, Amazons, and other nomads are like neutral warriors.

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The philosophy of Warlocks: "Light—it cuts the eyes too much. In the light, a person's flaws stand out especially brightly. But darkness is peace. In the darkness, all are equal. Darkness is everywhere. Only in the darkness will you find the true light."

A Warlock already exists—those are the Dark Elves. "We rule the shadow and the shadow rules the world"—don't those words sound familiar? Spiders in a city is nonsense; they are solitary predators everywhere.:)