"Flight to Salvation" - "The Veil is Torn" [Campaign 4, Mission 2]

After the ritual, the knight's Castle transformed into a demon Castle. It seems that all the accumulated knight units also turned into demons. The demons had a very large army. If I play again, Zephyr and his supporting heroes will fly around like bees and perform this ritual much earlier than this time.

The demon army remains unchanged until Frida and Duncan appear. Before that, the demon leader doesn't even leave the Castle. So, it makes sense for Zephyr to accumulate money and resources; they will be transferred to Frida and will be useful when building the human Castle.

A few notes:
1. The red units from the outpost in front of the human Castle can freely join Duncan and Frida's army, so don't pay attention to the small army they give you at the beginning, even with a powerful demon. Some of the red units on the map will also join (only the griffons didn't join me).

2. Note that the main demon Castle is guarded by two garrisons. But the armies in them are different; one is almost three times weaker than the other.

3. Try to level up Frida and give her all the composite artifacts (those that consist of several parts), as they will be transferred to her in the final mission, where she will assault one of the demon Castles.