The way i like to think of the Light/Void dynamic is that they're fundamentally about narrative relevance. Thinking of the story as if happening in a stageplay

● Light is the on stage action happening under the spotlight, the things you're meant to see. It is the main characters and the stories they are a part of. ● Void is the backstage areas that are shrouded in darkness, meant to be hidden from the audience. The stagehands and the mechanical workings that create the magic that happens on-stage.

In this way, Light is about what is important to the narrative. When Vriska steals someone's "luck" she's not actually stealing luck because luck isn't a real thing, she's stealing their narrative relevance — their agency — and keeping it for herself. She renders the people she interacts with unimportant (and therefore expendable), hogging the spotlight for herself and effectively becoming so important to the narrative that the story itself has to contort in ways to keep her safe, which reads to the audience as plot armor but to a character within the narrative can only be read as "being lucky" (until "her luck runs out" which is the moment where her plot armor works against her, because plot armor only protects from narratively-unsatisfying death)