Well, heroes with Darklings will move at a speed of over 30. Accordingly, development and map clearing will happen faster, by 8+ turns each time. So, let's calculate the lost days when a hero, twice as powerful as ours, appears.
half of the map will already be cleared before building the Darklings...
Added 4 minutes later
It's incredibly interesting how artifacts can increase the movement range of Hydras on the map. There's no need to give general movement modifiers as an example (boots, gloves, etc.), because simple calculations show that this will only increase the movement gap ;)
The numbers are as follows: in a standard setup, an army with Darklings has ~65 movement points, and an army with Hydras has ~51 (considering standard modifiers: Swiftfoot, Gloves, Boots). The more modifiers, the further behind the slower units fall.
what movement gap are you talking about?!
an army of hero + Darklings has exactly 30 movement points without artifacts and skills, I repeat, artifacts and skills increase the movement of the hero AND HIS ARMY on the map