Structural lore — what Oda has confirmed about this. Mysteries
(unsolved questions) live in Vault/Threads/; this is what the world IS.
What we know
Ch. 1179: The throne’s hidden occupant is captioned on-page as “KING OF THE WORLD — ST. NERONA IMU” — the empty-throne fiction is now formally contradicted by the narrator for the reader (in-world secrecy status unknown). See The Empty Throne Is Secretly Occupied By The Hidden Sovereign Imu.
Ch. 907: Located at the very center of the world inside Pangaea Castle, Sacred Marijoa. No one is permitted to sit upon it; that it stands empty is declared “a symbol of peace.”
Ch. 907: The kings of the various nations are “on equal standing,” each swearing an oath not to seek control over the others; there is no single king of the entire world. The greatest authority is the Five Elders.
Ch. 907: Guarded by 20 weapons, placed “as an oath… by the first 20 who created this world 800 years ago” — the founding twenty (cf. the twenty kingdoms / Celestial-Dragon origin, Ch. 722).
Chronology / structure
Ch. 0907 — the Empty Throne is established on-page during the Reverie: shown to attending kings (e.g. Stelly), framed as a “symbol of peace,” guarded by the 20 founders’ weapons.
Ch. 0908 — the throne in the Chamber of Flowers is shown occupied by “Great Imu” — the Five Elders kneel and serve; the seat the world believes is power’s empty center holds a hidden ruler.
Open questions about this topic
Imu Identity — who/what sits at the apex above the Five Elders, and why the seat at the heart of the world is framed as “empty.”