Auto-translated
A master class on annihilating a horde of undead (I had 779 of them) near Apel-Sina.
They can be killed without any losses to your forces if you have the ability to cast Phantom.
The key point: 1) These creatures – the undead – are large. 2) Obstacles to their movement always appear in battle mode. We will leave non-phantomizable high-level creatures (unicorns and ents) out of the discussion.

Cast Phantom on the dryads. They are good because they don't get hit in return. And with a successful hit, they take out 18 undead from each adjacent stack, i.e., 36 creatures at a time. One dryad goes to the upper passage and creates a Thermopylae for the creatures. That is, for large creatures to pass further, they must first kill it. The dryad's phantom blocks the lower passage.

You can also cast Phantom on the Death Dancers. However, this does not justify the cost. They are constantly killed on the first hit, despite all their phantom abilities.

While the undead are taking damage from the dryads, the archmages take out approximately 20-30 with one arrow, and the sorcerers take out 16. It is also good to cast General Speed. The main thing is to hide the living (non-phantom) creatures behind the phantom shield, and you will be happy. So, after a few turns.

It is already clear that the next wave of creatures will be enough.
Hooray, victory.

The only losses are the phantoms, and the Death Dancers died a brave death, practically without causing significant damage to the enemy.
The described method also works on Rakshasas (at the beginning of the map), with the difference that we give the dragon to the assistant, multiply the dryads manually, placing one dryad in all available slots, and in battle, we cast Phantom on ten archmages. While the Rakshasas break through the butterfly barrier, the phantom archers successfully destroy them. Losses – 5-6 dryads.
Off-topic, I will add that unicorns are useful in battle against a mage: the magical defense of neighboring units increases significantly.
They can be killed without any losses to your forces if you have the ability to cast Phantom.
The key point: 1) These creatures – the undead – are large. 2) Obstacles to their movement always appear in battle mode. We will leave non-phantomizable high-level creatures (unicorns and ents) out of the discussion.
Cast Phantom on the dryads. They are good because they don't get hit in return. And with a successful hit, they take out 18 undead from each adjacent stack, i.e., 36 creatures at a time. One dryad goes to the upper passage and creates a Thermopylae for the creatures. That is, for large creatures to pass further, they must first kill it. The dryad's phantom blocks the lower passage.
You can also cast Phantom on the Death Dancers. However, this does not justify the cost. They are constantly killed on the first hit, despite all their phantom abilities.
While the undead are taking damage from the dryads, the archmages take out approximately 20-30 with one arrow, and the sorcerers take out 16. It is also good to cast General Speed. The main thing is to hide the living (non-phantom) creatures behind the phantom shield, and you will be happy. So, after a few turns.
It is already clear that the next wave of creatures will be enough.
Hooray, victory.
The only losses are the phantoms, and the Death Dancers died a brave death, practically without causing significant damage to the enemy.
The described method also works on Rakshasas (at the beginning of the map), with the difference that we give the dragon to the assistant, multiply the dryads manually, placing one dryad in all available slots, and in battle, we cast Phantom on ten archmages. While the Rakshasas break through the butterfly barrier, the phantom archers successfully destroy them. Losses – 5-6 dryads.
Off-topic, I will add that unicorns are useful in battle against a mage: the magical defense of neighboring units increases significantly.