Robin had answered with a truth she hated: "It's the mall's heart. All that concrete, all that electricity, all those people feeding it every day... something woke up when the Flayer died. It left a seed."
Steve blinked. "That's... actually smart." stranger things season 3 episode 8 runtime
Here's the answer to your first request, followed by an original story as you asked. Robin had answered with a truth she hated:
It had started an hour ago. The lights in the mall had flickered red. Then the mannequins from GAP—every single one—had turned their heads in unison. Not toward the exits. Toward the floor . all that electricity
"No. I'm gonna suggest we blow the food court gas line."
The "new thing" was not the Mind Flayer. They’d seen that. This was different. Smaller. Faster.