(The “island rides a living elephant” core lands Ch. 806 when the elephant’s body is shown — but the walking / sentience / speech reveal is forward, and the Void-Century tie is forward. Keep pending until the elephant’s nature is paid off on-page; downstream chapters (0803, 0805) merge their duplicate seeds here.)
Why this matters
A background-symbol + chekhov-explicit double-seed: the destination is literally a living, millennium-old creature, and the round-number isolation of its inhabitants is foregrounded the instant the island is shown — Oda clustering Void-Century-adjacent timeframes onto one set-piece.