Malachi had often wondered just how interchangeable his powers were.
It was a natural thing to consider when one took a moment to think about the breadth of abilities at his disposal and their various potential uses.
Was he using them at their most optimal? Was there a hidden niche that he could be unknowingly missing?
Ordinarily, Malachi would have consulted Rowan for this, but the old man was rather busy these days, and Mal didn't want to add any more to his plate.
So, he was reduced to discovering different things on his own. Usually, the beginning of a new discovery started with him thinking, 'Huh. This might be cool.' or participating in a powerscaling debate with Bianca.
His current state was the culmination of both sources of inspiration.
Swapping out his darkness for lightning, Malachi became a living beacon who turned the dark sewer into a tunnel of light.