Kwasi
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Personally, when playing as Inferno, I always choose Marusha as my main hero and prefer to give her the Fire spell for mass casting. With the casting skill, gathering resources and completing tasks becomes easy (especially if you have one turn). Plus, Marusha has armor-piercing damage, which makes dealing with neutral creatures a breeze.
(And Marusha's special ability is great!)
I prefer to start with Calh. And if you don't hit me with a better hero, then it might even be my main hero.