Defensive gameplay and other tactics.

After you’ve defeated them, you should blind them, slow them down, and apply a vulnerability debuff, reducing their defense to 0. Then, use the Necromancer’s Mark and skillfully eliminate them bit by bit with units they can’t retaliate against – vampires and air elementals (if you have them), as well as their clones. You can now spend mana freely on summoning, raising the dead, and blinding, because the Necromancer’s Mark is in place.

After attacking the blinded cyclops, the blinding effect wears off, so you need to time it so that your hero moves in front of the cyclops, but this doesn’t always work. The damage that the orcs will inflict on the cyclops is incomparable to the damage that my troops will inflict on them, because their weakest unit is stronger than my entire army. By attacking with orcish troops, you kill two birds with one stone: you reduce the number of cyclops and also weaken the other units. I didn’t have any air elementals, and I doubt they could inflict significant damage on the cyclops. I agree that phantoms are very useful for providing cover.