The Void Century’s greatest mystery is finally coming to light as Oda drops massive hints about the ancient conflict. To understand the current stakes in Egghead, we must first uncover the secret of Joyboy and his ultimate downfall.
Recent revelations suggest that Imu doesn’t just rely on political power, but a terrifying ‘Supreme Demon’ ability. This power was specifically designed to counter the freedom of the Nika fruit during the original war 800 years ago.
What is the ‘Supreme Demon’ power behind how Imu defeated Joy Boy?

While many fans have theorized about the Doi Reversy ability, it appears this is only a fraction of Imu’s true arsenal. The ‘Supreme Demon’ power is described by Elbaph’s ancient texts as a force capable of dominating the entire world and suppressing the Sun God Nika.
This power likely allowed Imu to manipulate the very nature of his enemies, turning their strengths into weaknesses. Key aspects of this power include:
- Nature Alteration: The ability to ‘reverse’ or dominate the will of others.
- Demonic Summoning: Calling forth weapons and powers through a mysterious national treasure.
- Immortality Granting: Ensuring his subordinates, like the Gorosei, can never truly fall in battle.
By using these forbidden techniques, Imu essentially locked Joy Boy into a battle of attrition he could never win. You can read more about Imu’s identity and the will of Joy Boy to see how this ancient grudge still fuels the World Government today.
Did the National Treasure of Mary Geoise explain how Imu defeated Joy Boy?

A massive theory circulating the community involves a ‘forbidden book’ that serves as the National Treasure of Mary Geoise. This book is believed to contain an arsenal of demonic powers that predate the existence of Devil Fruits themselves.
If Imu had access to every demonic ability in existence, Joy Boy’s Nika fruit would have been overwhelmed by sheer variety. This tactical advantage is likely a core reason for Nika’s first defeat centuries ago.
- Weapon Storage: Imu can seemingly manifest weapons directly from this ancient source.
- Power Nullification: The treasure might act as the original source of the ‘Sea’s Curse’.
- Strategic Dominance: Imu used this arsenal to maintain planetary control for 800 years.
Is high-level Conqueror’s Haki the secret to how Imu defeated Joy Boy?
Recent flashbacks to God Valley show that combat skill alone isn’t enough to stop Imu’s chosen warriors. To truly injure an immortal with high-level Conqueror’s Haki, the attacker must possess an even greater spiritual force.
Imu’s Haki is likely at a level that transcends anything we have seen from the Yonko or Admirals. This overwhelming pressure, combined with immortality, created a ‘wall’ that even the original Joy Boy could not break through. This explains why current events are leading to a massive Elbaph war involving Imu as the giants hold the key to killing immortals.
Can Luffy Succeed Where Joy Boy Failed?
The history of how Imu defeated Joy Boy serves as a warning for Luffy and the Straw Hat crew. Brute force won’t be enough; they will need to solve the mystery of Imu’s demonic form and perhaps find an unlikely ally. Will Blackbeard’s nullification powers or Loki’s secret treasure be the deciding factor in the final war? Let us know your theories in the comments!