I Quietly Kept a Human as a Pet

Nie Li claims to be Earth's guardian. A 17-year-old human-shaped being with terrifying powers of destruction and control, she has destroyed contact between Earth and alien civilizations 96 times during her 17 years of existence. She has protected Earth's safety, but also eliminated the possibility of its rapid development. She thinks she's protecting humanity, but in reality, she's keeping them in a cage. Content warnings: 1. The female lead is the strongest. 2. There's a tiny bit of romance. It doesn't appear anywhere in the author's outline, anyway. 3. The female lead isn't human. 4. Please don't connect anything scientific to reality. It's all based on the author's Wiki browsing and imagination. Point out any logical errors, but there's no need to mention scientific inaccuracies... Updates whenever inspiration strikes. The author has a busy life and is under academic pressure.