Livestock?

<Bloodcrest Empire - Demon City>

This place was smaller than Summit City by a lot, and unlike its warm, inviting glow, this realm was perpetually shrouded in darkness, trapped in eternal night.

The demons dwelling here sustained themselves solely on blood, making the human population of over 500,000 merely a resource to be tapped for their monthly supply. 

The surplus blood served as a valuable commodity, traded with neighboring Demon Cities in the vicinity.

Normally, such treatment of humans as livestock would be deemed inhumane. 

However, the Demon Lord governing this realm had made adjustments to sustain the operation of this city.

She recognized the importance of balance and understood that stressed and unhealthy humans would not be able to regenerate blood as quickly. 

That's why she imposed a law to ensure that such mistreatment never occurred.