The fourth stage of the "Van Kanighem" tournament.

I would first like to ask what general methods were used in the battles. Summoning fairies, haste, poison, beholders — that's clear, but what else? For example, I didn't immediately understand how to kill the vamps and mummies [44,35], or the devils and aberrations [92,49].

I'll answer in general for now.
1. On the map at the start of the game, there is ONLY ONE bottle of slowing liquid, which also clips the wings of flying units. I specifically saved this bottle for the fight against the vamps near the gold mine with a bunch of Troglodytes. Regular slow doesn't work on vamps, and beholders won't slow them, but if you blast them with this bottle, they will be slowed by half, and their wings will be bound, which is very helpful. Mummies run roughly the same as slowed vamps. Therefore, add haste to the hero and the battle is won in the standard way. If you need details, let me know, and I'll have to check additional saves. Look in the hero's inventory before and after this fight; you should see that I spent this bottle specifically on this battle.
2. Devils and Aberrations — that's a story about the hero class: Witcher. Read somewhere in the game menus; if you hover the mouse over the hero, it will tell you what property the Witcher possesses. In this walkthrough, I had TWO Witcher heroes. The class is obtained as follows: if, among all skills, two outweigh the others — Chaos and Nobility (they have the most colored corners and more skill line slots used), the hero is assigned the Witcher class (look at the skills of the heroes who fought the devils). The Witcher's strike is famous for the fact that an army without immunity to mind magic does not counterattack and retreats from the hero by two cells in fear, thereby being unable to deliver a counter-strike. However, when a neutral unit strikes the Witcher first, the hit lands. To prevent this, you need to acquire the corresponding FIRST STRIKE magic. Or level up the combat skill to the necessary level, but in a way that doesn't change the hero's class. On this map, there was Chaos magic "First Strike". Now, when you have such magic, the enemy cannot even hit you on their turn if it is cast on you. They want to strike, they approach, they swing, but the Witcher delivers the counterattack first. And since the enemy then retreats two cells, they never actually hit :) A beholder was brought to the fight, and the hero drank a bottle of immortality before the battle!! The Devil flies up to the Witcher and cuts him down, but he jumps back up due to the doping. On its turn, the beholder breaks the BOW of the aberrations. On his turn, the Witcher hero casts FIRST STRIKE magic on himself. That's it. Considering load-saves in battle, the opponent has no chance. The Devils are constantly getting beaten and cannot hit the Witcher, the aberrations crawl slowly, especially on their own turn; while they crawl, you can cast haste on yourself and slow on them, and for added effect, you can poison both squads. Then the main thing is to move across the field so that only the Devils can try to hit you; otherwise, you won't be able to perform a counterattack against the second attacking squad because it will be removed by the first attacking squad, and as a result, you will take a hit. One more point: in some cases, even a Witcher hero can take a hit:
1. The enemy has nowhere to retreat two cells — an obstacle, a unit, or the edge of the map is in the way. Maneuver correctly :)
2. It seems that if the Devils suddenly wait on their turn, they will then deliver two strikes, and your counterattack will not recover. In this case, a load/save in battle helps. Don't let the Devils wait, and that's it.
At the end of the battle, the Devils summoned Ice Demons, but that no longer mattered; both slow and poison work on them as well.
I think I've answered these battles in full. By the way, if anyone is interested in this fight, I can prepare this save before the battle so you can try to break through the Devils yourselves ;)
There were some other difficult battles. For example: Beholders cannot break the bows of ballistas and flamethrowers. And if they work in tandem with infantry, I couldn't win, because at that moment the heroes had likely not yet obtained the Witcher class or didn't have first strike magic. Therefore, I had to scrape together units of archers (medusas and orcs) from every corner :) In battle, all units were lined up in a single line using a special formation before the attack. Then the hero constantly summoned fairies, and they stood at the beginning of the chain, shielding everyone from the ballista shots. And the archers cut off the infantry; luckily, medusas have infinite arrows. I managed to avoid fighting the flamethrowers entirely. Almost everything near them was taken without a fight. There were also some small problems with mages and genies, and with neutral elf troops and the Thief near the pyramid by the harbor. By the way, a double-strike tactic against the army was used there (thank god in 4 no one disappears from the army after artillery preparation :) There is a tactician hero there. And all his units run fast. I had to first beat their commander with flamethrowers (magic) so that he had enough health left for only one magic shot. On the second attack, we kill their commander first, and the enemy troops are out :)
PS. I didn't use Minotaurs during the walkthrough. Beholders turned out to be better. Minotaurs cannot overcome medusas, because whenever neutral medusas shot at my minotaurs, a magic hit always went through, even if they blocked the shot itself. If anyone used minos — did you manage to purely deflect a medusa strike with minos even once ??