Chaos structures.

and then you can solve it with artifacts)

It's incredibly interesting how you can increase the movement range of Hydras on the map using artifacts. There's no need to give examples of general movement modifiers (boots, gloves, etc.), because simple arithmetic calculations show that this will only increase the movement difference ;)

Here are the numbers: in a standard setup, an army with Champions has ~65 movement points, while an army with Hydras has ~51 (standard modifiers are considered: speed boots, gloves, and the chariot). The more modifiers, the further behind the slow units fall.