Scripts

SetGameVar("Raelag", geroy);

What kind of magic is this?! It's enough to write main_hero = 'Raelag'. SetGameVar is used to transfer variables from script to script and through campaign missions.
In battle, the hero's name can be easily and simply found using the GetHeroName function, so it can be simplified, and a hook for the start of the battle needs to be added.

function Start()
    if GetHeroName(GetAttackerHero()) == 'Raelag' then
        print("if the main hero is the attacker");
        local mana = GetUntiManaPoints(GetAttackerHero()) --Otherwise, we will leave 200 mana for the player for no reason!
        SetUnitManaPoints(GetAttackerHero(), 200);
        repeat sleep(1) until GetUntiManaPoints(GetAttackerHero())==200 --Sleep until the mana is added
        UnitCastAimedSpell(GetAttackerHero(), 4);
        SetUnitManaPoints(GetAttackerHero(), mana); --Return the mana to the amount it was!
        print("casting");
    elseif GetHeroName(GetDefenderHero()) == 'Raelag' then
        print("if the main hero is the attacker");
        local mana = GetUntiManaPoints(GetDefenderHero()) --Otherwise, we will leave 200 mana for the player for no reason!
        SetUnitManaPoints(GetDefenderHero(), 200);
        repeat sleep(1) until GetUntiManaPoints(GetDefenderHero())==200 --Sleep until the mana is added
        UnitCastAimedSpell(GetDefenderHero(), 4);
        SetUnitManaPoints(GetDefenderHero(), mana); --Return the mana to the amount it was!
        print("casting");
    end;
end

The script error is very strange, as if your MapScript is also running in battle: there is no such function in tactical mode, and therefore an error occurs. Can you attach both script files? Upload them to Google/Yandex Drive.