Let’s come up with new “war machines.”

The question is, how do you envision this? Archliches attack with Death Cloud and Fireball... And considering that everyone has a different number of mages, I wouldn't want the Academy – their 4th-level archmages – to cast Fireball during a normal attack...

Then, let's make an adjustment: spells of levels 1 and 2 are cast.
Another adjustment: spell damage only occurs when the mage fights in melee.
We can also create a hero skill in "Machine Management":
"Magical Madness" - if the hero has a crystal ball, the mana cost for casting spells is randomly reduced by 25-50%. In addition, each creature recovers 10% of its mana reserve each turn (the hero recovers 5% of mana).