>>532226784
It could psychic power called Smite, majority of psykers know it, according to some sources. It takes various forms, lighting included.
I wish RT's psykery wouldn't be restricted by staves and were closer to original source
Also, in some sources (like in Dark Heresy 1st ed) lightning IS a biomantic power. And Dark Heresy 2nd ed makes Smite a biomantic power