You might also look to a choice of magics and A Wizard in Rhyme serious by Christopher Stasheff for inspiration. Now I’m usually a omnicidal maniac. But why just destruction? Why not conquest? And I the hero side just traditional kissing babies and killing Monsters or will they have more nuanced motivation like money or wanting to fight the best to get stronger aka the Goku/Vegeta motivation ?
After playing this, this now remind me of the anime, “Tensei shitara slime datta ken” or “That Time I Got Reincarnated as a Slime”.