What spell combinations are there?

I said "at the beginning of the game," when the hero is still far from having level 4 spells (cat-like reaction), but getting a level 1 spell from the opposite school is quite possible. Also, at the beginning of the game, there are few Medusas, and for petrification to work, the Medusa squad needs to have a 50% chance of killing at least one unit from the enemy squad; the probability decreases as the level of enemy monsters or heroes increases. To use an infinite supply of ammunition, you need to prevent the enemy from engaging in melee combat, which is also problematic at the beginning of the game.