So after re-reading Vol 6 Chapter 1 a doubt cross my mind

Ok… Uh, hmm, speaking of which, uh, what’s Demiurge-san doing right now?”

“He’s conducting a breeding experiment. Humans can breed with each other, but can’t breed with demi-humans. Is this not a true tragedy? For lovers to be unable to bear the fruit of their union just because they’re from different species! To save such unfortunate souls, Demiurge-sama is working hard. To develop that possibility between humans and demihumans!” The clown spoke as if he was reciting a speech with both arms wide spread and pointing at the sky. Mare blinked at Pulcinella, who changed so suddenly. “Ah, please excuse me. I’ve gotten too excited over Demiurge-sama’s generosity of trying to bring joy to humans. Please, forgive me.”

“Ah, it’s, uh, fine.”

“Demiurge-sama said that he would make himself —or rather the demons— the target of the human’s hatred, so they wouldn’t resent each other. Such immense selflessness! This Pulcinella cannot even see because he moved me to tears.” Pulcinella motioned to wipe his tears on top of his mask. Of course, there were no actual tears and he spoke in his regular cheerful tone, which didn’t sound sad at all.

“…Why would they hate him?”

“I cannot understand why they would hate our kind and generous Demiurge-sama, but he said that himself. Ah, speaking of which, listen to this. Because Demiurge-sama was so generous, he took pity on the starving livestock. So he made them exchange children with each other, roasted them and put them on the table. If he was heartless, wouldn’t he have served them up without exchanging them?”

“I-Is that so?”

“Of course. He even allowed them to say farewell by bringing over both parents and letting them sit by the table… For there to be someone like Demiurge-sama, who would be considerate enough for the family to say farewell while smiling… There won’t be anyone besides the Supreme Beings. I’m sure of it.”

“I guess…” Mare gave a flat response to Pulcinella’s enraptured speech. He didn’t care what happened to anyone who did not belong to Nazarick. After a couple of seconds, Mare erased all thoughts of Demiurge’s livestock.

“Plus, when starving, their head might say yes, but their stomach might not. Demiurgesama thought ahead and after warning them, made sure they ate it all, down to the last bit. He is a truly generous…” Feeling that the story would not end, Mare quickly interrupted, “…H-how’s Guren-san doing? If I want to send the message back, I might need to relay it to him, but I don’t know what he’s doing and where.” - Volume 8

Demiurge is operating a concentration camp-like facility, where humans and demihumans are brutally tortured and forced to partake in cruel experiments.

/r/overlord Thread