In the Nine Provinces World, a Buddhist School master had once divided all living things into three kinds.
Unknowing, Sentient Beings, and Evil Fiends.
Plants in the mountains, ants, mosquitoes, and the like had only the instinct to live, without the Wisdom to think. They knew nothing, understood nothing, were neither good nor evil, and could not even comprehend life or death. Such creatures were called "Unknowing."
Above the Unknowing, naturally, were those who knew.
But those who knew fell into two broad kinds. One understood its own existence, knew to seek advantage and avoid harm, and could feel love and hate. Such creatures were "Sentient Beings." The other possessed Wisdom too, but its greed and malice overwhelmed it. It wallowed in plunder and predation, knowing only how to destroy and not how to create. These were called "Evil Fiends."
Most monsters were Evil Fiends. If something tasted good, if eating it offered some benefit, they could not resist even when they knew it was poisonous. When the Northerners hunted monsters, they often used blatantly poisoned bait. Hidden inside things that looked awful at a glance were ingredients beneficial to Evil Fiends. Any Evil Fiend that saw one would eat it. It worked every time.
As for monsters that could restrain their greedy nature, they were no longer Evil Fiends but Sentient Beings one could speak with. There might be conflicts between them and others, even frequent fights to the death, but given the right conditions, they could compromise and live in peace.
The Lesser Monsters that had swarmed in to devour the Blackwater King's corpse belonged among the Evil Fiends.
Did they truly not know the Blackwater King's corpse was poisonous? Not necessarily.
But for monsters, devouring other monsters could help them grow stronger. Intelligent monsters understood that this