Ball of Lightning is THE BEST pet dragon ability, but it takes some work to have it shine. It doesn't cost much rage when maxed, and kills a proportion of the squad, just like Reaper's ability in KBTL. Top it up with some gorguanas and Mark of Blood and you can kill up to 96% of the stack in one go.
However, at the start of the game, Ball of Lightning is somewhat weak, because the stacks are small and it won't do much on its own.
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