I'm talking about a quantity of around 200-300. It's not difficult to counter Archliches. There are more problems with archers, that's true. A lot also depends on the starting attributes; Necromancer archers or Demon heroes come out earlier. Melee units generally won't reach the demons in Necropolis. Chaos can be different. If it's a meteor shower, that's bad. If it's a ring, that's a bonus; the damage from a ring to a single target isn't very high. While he's throwing Chaos at the demons, the rest of the army won't take much damage. After all, a ring aimed at one stack of summoned black demons and two stacks of real demons differ significantly in effectiveness. By distracting the hero, the black demons will be more useful.