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I checked in the editor – the champion of the neutral faction has three times more stats than a regular unit. That's why there are 75 Bulls, 90 Medusas, 36 Ifrits, and 24 Unicorns. There are 6 Monks in the dwelling and 5 Crusaders; the weekly growth in the field dwelling is twice as slow. Considering that the neutral faction has a higher growth rate, and it starts not from the moment the dwelling is captured, but from the beginning of the scenario, it won't be possible to accumulate a large army of Monks and Crusaders. However, it should be noted that the team has 3 of the best magic schools, but it is desirable to upgrade them – Life at least to level 4, Order and Nature to levels 2-3 (as possible) and acquire the necessary spells. And before the battle, buy Body Armor in the forge. Form a square formation – and into battle. Some enhance their own, others slow down the enemy, and the Monks and Crusaders act as a living shield. Medusas are very dangerous – they can kill any hero, and this must not be allowed. And Hit-and-Run tactics won't work here; you need to rely on a tank. Warfare and Melee skills at level 5 are just right. Ranged attacks won't help, because melee combat is inevitable, and the damage will then be minimal.
Usually, each scenario has 1-2 key battles, after which the rest no longer pose a problem.