Chainsaw Man's latest chapter recently dropped and War Devil Yoru's grand scheme for mankind was finally revealed. Prior to this, there was massive speculation about her ultimate goal, given her vague actions. However, the return of Nuclear Weapons in chapter 210 altered the plot's landscape considerably. Yoru has now gained a near-immeasurable power due to the growing fear of war.
This, needless to mention, stems from America reinventing and dropping atomic bombs on the Soviet Union. Curiously, Denji looks to be in a sort of limbo, meeting the Death Devil there. She is the one who reveals Yoru's plan for humanity and it is worse than what the Nostradmus Prophecy foretold. In simple words, Yoru wants a world with never-ending chaos.
Chainsaw Man: The War Devil's baleful plot is more terrifying than the Nostradamus Prophecy

Before diving in, it is worth mentioning the Nostradamus Prophecy. The prophecy, also mentioned by the Death Devil (then posing as Fami), puts forth that in the seventh month of the year 1999, a Great King of Terror will descend upon the Earth and spell the end of humanity, to usher in a new age of Devils. The "King" in question was to be the Death Devil herself.
Now as Chainsaw Man chapter 211, Lady Death arrived earlier than expected and had been working towards stopping the prophecy. She wanted to change that predicted future and her powers from activating. However, the War Devil gaining such a significant upgrade derailed things entirely. Now, even though that future had changed, it become something worse.
As the Death Devil explains, the surging fear of war due to nuclear weapons being unleashed made Yoru stronger than the former expected. Moreover, the War Devil had already kicked off her plan - she was killing Devil Hunters whilst gathering an army of Devils. Further, she would soon find Denji and turn him into a weapon, her main target being her sister, the Death Devil.

Given Chainsaw Man's Erasure powers, the weapon Yoru thus forms would be capable of wiping out the Death Devil. As per series lore, and Death's own words, this would mean that the concept of death would cease to exist. In other words, living beings become unable to die from any known causes, like illness, old age, injury and so on. They would essentially suffer till cured/healed.
A world like this would turn into an absolute nightmare - endless suffering, hate and conflict in a scenario where one cannot pass away, a "never-ending World ar II". Diving deeper into this, such a world would be far worse than any apocalypse. Devoid of death's release, suffering becomes infinite - physical pain never heals, mental traumas persist and social conflicts stagnate and continue endlessly.
In this war-like situation, individuals cannot die, only be maimed and left to writhe in agony. Resources dwindle, populations boom uncontrollably and a brutal scramble for survival ensues. Pain caused from physical, mental or emotional turmoil never heals and any hopes of peace would be lost forever amidst the cloud of chaos.

More than pandemonium, the world may turn into a twisted parody of life itself. Cultures would stagnate and eventually disappear as oppressive powers (in this case Yoru and her Devil army) reign unchallenged. Gradually, battles become less strategic and more of a last man standing cage fight where combatants are doomed to never achieve victory or death.
Additionally, even petty squabbles can grow into endless cycles of revenge, with neither party having the option of exiting the board. A reality like this knows not what mercy means, or rather forgets. It is replaced by a dark eternity of mutual torment - a world trapped in a circle of hatred, time flowing with nothing ever truly changing.
Final Thoughts

To conclude, the War Devils' vision for Humanity in Chainsaw Man represents destruction coupled with the erasure of any kind of relief or peace. By wiping out Death, she would be condemning the world to an never-ending loop pain and suffering, where injuries, grudges, and injustice do not cease to exist.
Needlees to mention, the natural cycle of life would be done away with and what remains would be an immovable, overpopulated, and resource-deprived existence. Wars drag on endlessly, nevermore for territory/ideology, but only to further violence with no finality in sight.
With Yoru at the helm in Chainsaw Man, suffering may become the new normal, stripping away the essence of life. In this manner, War Devil Yoru's grand scheme far exceeds what the Nostradamus Prophecy posited. It feeds into an apocalyptic fate that is eternally and irredeemably inhuman.
Related links:
- One of Chainsaw Man's most beloved characters was inspired by Tokyo Ghoul
- Yoru manages a feat in Chainsaw Man chapter 210 that even Makima never could
- Fujimoto might pull a Fire Force type ending with Chainsaw Man (and it would be absolute cinema)