psatkha
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You need to look for them, but the existence of combinations that create synergy is a fact!
For example, I once gave the Inferno faction the Fire Wave spell, and what do you think happened? - a synergistic combination Fire Wave - Slicing Sword was created - everyone touched by the wave was also affected by the sword.
Good if that's the case!
If there are such bonuses from simultaneous use, then of course they should be included in the formula!
As far as I remember, it increases Power and Cost, and also decreases Growth!
С уважением, Psatkha (Псатха) 
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