Unscheduled fiction, inspired by the prompt at TVS Monthly Nanofiction Bonanza. Not 55 words, I am disqualified, but these two characters wanted to emerge so I let them out.
At the top of the stairs, Sonja watched as Milo snapped the switch into the "On" position. The basement below remained dark. Milo grunted. He snapped the switch off, than on again. "Nothin'", he muttered. He began to snap the switch back and forth in rapid succession. Sonja counted fourteen clicks before she reached out and slapped his hand down. Milo yelped and jerked back. One foot slipped down a step, and he sat down hard to keep from tumbling. He opened his mouth to whine at her, then shut it tight at the sight of her stony face.
She let him sulk for a moment, then asked, "Have you ever heard of the butterfly effect?"
Milo's pout was a mixture of surprise and wariness. "Yeah, sure. If a butterfly flaps its wings in Japan, you get a hurricane in Miami."
"Wrong." She tapped the switchbox with a clean, unpolished fingernail. "Each time you clicked this switch, a butterfly species became extinct. You just killed off seventeen species of butterflies."
She knew Milo could see in her eyes that she was serious. A steel-blue glint always appeared in her left eye when she was telling an unvarnished truth. She had a gift for telling half-truths and outright lies, which was an unexpected talent for a malak. She was uncomfortable with how beautifully she could lie, so she had installed a sword-gleam in her eye to let others know when she was speaking the perfect truth. Still, a person had to know her for a period of time, and be observant, to be able to catch the tell.
Milo had known her for only three months, but his awareness had improved to a remarkable degree since the day she first manifested to him. His ignorance was still exasperating, but his potential was immense. Typical human.
"Seventeen species...oh, god, why didn't you stop me sooner?" Milo was wailing.
"Because it's against the rules for me to stop you. That would interfere with your oh-so-glorious human agency. Seventeen is the magic number. With any particular bit of ignorant assholery you get seventeen chances to stop on your own. After that, I can step in--and not just me. If I'm not around, any member of the malakhim can stop you, which might not be so lucky for you. Other malakhim don't have my patience. If they're not your guardian or teacher, they will just dispatch you into your next incarnation."
"You mean...they would kill me?" asked Milo. Sonja still found it interesting to watch how human beings changed their faces to communicate their feelings. In moments, Milo's skin had become more pale, with a peculiar green cast. The change was not as dazzling as the effects produced in some cephalopod species, but the range of subtleties were definitely entertaining.
"Yes, of course. Killing you would take the least effort, and be the most efficient. A simple change of state, one of the simplest."