The world of One Piece has some of the most complex world-building in anime. Spanning over a thousand episodes and counting, the world-building in One Piece is filled with hundreds of moments that offer insight into key details just beneath the surface. With so much depth, it can be easy to get lost in the finer details and even forget certain key aspects of Oda's finely crafted world because of how many twists and turns that completely shift the lore and plot of the story.

While some world-building elements have yet to be fully explored, other elements have brought rich detail to the narrative for fans to theorize and debate. Some have even changed the scale of the story itself or added even more mystery and questions.

10 Haki can Damage Logia-Types

Logia-Types Were Once Invincible

Ever since the first Logia-Type Devil Fruit hit the screen, fans have pondered over just how powerful some Devil Fruits are in the story, especially early into the Straw Hats' adventure. Smoker and his Plume-Plume Fruit brought Luffy to the brink of capture, and was considered an impossible challenge for Luffy to overcome. Being made of smoke or any non-tangible substance is ridiculously overpowered and while having a challenge for Luffy to surpass is good, making that challenge seemingly impossible can only work with the best thought out system.

Luckily, Oda thought of that and introduced Haki, One Piece's secondary magic system. Haki itself is broken into three different categories: Observation Haki, Armament Haki, and Conqueror's Haki. Each has its own set of rules and limitations, but Armament Haki is what gives Luffy the ability to land an actual hit against Logia-Types and make them tangible. Considering Logia-Types were nearly invincible up until the point in the story where Haki was introduced, they served their narrative purpose as invincible forces of nature, perfectly.

9 The Apology of Joyboy

What Happened During the Void Century?

The name Joyboy has significant symbolism and meaning in One Piece, and has led to countless fan theories surrounding the mysterious character. While not much is known of who Joyboy was or what he looked like, what is known is that he left an apology on a Poneglyph to the people of Fish-Man Island for failing to honor his promise. While not much is known about the finer details of his promise, it was significant enough for him to leave a Poneglyph behind.

Joyboy has a connection to Nika and Luffy's Devil Fruit. As the story enters into its final saga, much is left to learn about the mysterious character, but some fan theories believe Joyboy was part of the Giant race. The only evidence within the lore is the giant straw hat that the elusive Imu has frozen. Joyboy lived during the Void Century and was somehow connected to the Poneglyphs and an ancient, advanced kingdom. Joyboy is arguably the most important character within the lore and worldbuilding of One Piece.

8 Noah and the Sea Kings

The Ancient Ship Sleeps

During the Fish-Man Island arc, the grand ship Noah was introduced and has left fans puzzled for years over its purpose. What is known about the massive ship is that Joyboy once made a promise to the people of Fish-Man Island to one day bring it to the surface, but he broke his promise for an unknown reason. The only ones who seemed to know anything about the ship's history were the sea kings.

The sea kings are one of the most dangerous forces on the sea, especially the Grand Line. But, unlike most other sea kings in the story, the group seen during the Fish-Man Island arc seem to remember what occurred during the Void Century and possibly even knew Joyboy himself. They helped move Noah to safety after it almost crashed into the island and knew about the true purpose of Noah.

7 Prophesy of Luffy Destroying Fish-Man Island

Shyarly's Predictions are Never Wrong

One of One Piece's most interesting revelations was the prophecy made by the mermaid Shyarly during the Fish-Man Island arc. She predicted that a man in a straw hat would one day destroy Fish-Man island. Presumably Luffy, but with recent events on Egghead, it's hard to say if Luffy will be the one to destroy the island or if it will be someone else with a straw hat.

While the idea of Luffy destroying an island is a hard sell to many fans, others have speculated that Luffy could potentially destroy the island. As of now, it's hard to imagine the Straw Hats backtracking to Fish-Man island this late in the story, so it's looking more likely that Luffy might not be the one to destroy Fish-Man Island, and predictions and prophecies tend to be a bit misleading with their definitions. It's possible that the destruction of Fish-Man island won't actually destroy the island itself, but without going into speculation, it's safe to say that Luffy most likely won't be returning to the island soon when the Straw Hats are so close to the final island.

6 The Ancient Weapons

Ancient Weapons That Slumber

Super weapons with the potential to conquer, even destroy the world, wait for the day they will again awaken. Pluton, Poseiden, and Uranus. Fans first learned about the ancient weapons' existence during the Alabasta arc where the Warlord of the Sea, Crocodile, was searching for Pluton's location with the help of Nico Robin. The Ancient Weapons' purpose in One Piece isn't clear yet, but they will definitely appear in some form by the end of the saga and will no doubt change the world when they awaken.

Pluton is a giant battleship said to be capable of destroying an entire island. Whereas Poseiden is a power that can control sea kings, and it only awakens in a mermaid of the Ryugu Kingdom on Fish-Man Island every few centuries or so. The current wielder of the power is princess Shirahoshi. While Uranus has yet to appear in the series.

5 Gol D. Roger Left a Message Behind in Skypiea

Oden Wrote the Message

Early on within the Grand Line, the Straw Hats reached Skypiea, an island floating above the clouds. During their adventure on the sky island, Nico Robin discovered a Poneglyph with an added inscription on the side, seemingly written by the pirate king himself, Gol D. Roger. Twenty years prior, the Roger Pirates also visited the island and left behind a message written in the same language as the Poneglyphs.

Up until recently, it was a mystery as to how Roger was able to leave a message behind in the ancient language, but with recent revelations, it was revealed in a flashback that Kozuki Oden, a samurai and daimyo from the Land of Wano, had accompanied the Roger Pirates on their quest for the One Piece. Especially early in the series, the idea that the king of the pirates had visited the island prior and was connected to the Poneglyphs added to the mystery and expanded the lore. Plus, it created a great contrast between Roger and Luffy's adventure.

4 Devil Fruits can Awaken

Let the Power Scaling Begin

Most shōnen anime have power-ups at some point in their story, and One Piece is no exception. Devil Fruit posses the ability to awaken, a process where the user experiences a significant upgrade in both power and ability that lets their Devil Fruit reach its true potential. Not many characters in the series have thus far awakened their fruit, which shows just how rare awakening are in the narrative.

Devil Fruits are already extremely fun, narratively speaking. They let Oda run wild with all the wacky powers, but awakenings allow for even more depth to an already complex magic system. And since Luffy has awakened Gear 5, there are sure to be more Devil Fruit awakenings for Luffy and the Straw Hats to face before the series eventually ends.

3 Devil Fruits can be Artificially Made

In More Ways Than one

Devil Fruits are one of One Piece's greatest story elements. They come in all shapes and sizes with just as many possible abilities to be showcased across the series, and artificial Devil Fruits add a fun twist to an already complicated magic system. During the Dressrosa arc and eventually the Punk Hazard arc, fans learned of the existence of artificial Devil Fruits known as SMILEs. Created by Caesar Clown and manufactured by the Warlord Donquixote Doflamingo for the purpose of creating a super army of Zoan-Type Devil Fruit users for Kaido and the Beast Pirates.

While SMILEs were exclusively Zoan-Type artificial Devil Fruits, another type of artificial Devil Fruits exist. Created by Doctor Vegapunk for his Seraphim project, he successfully created artificial Paramecia-Type powers using blood from existing users. The added element of artificial Devil Fruits expanded the already massive roster of known fruits to an absurd degree.

2 The Empty Throne Isn't so Empty

Imu Secretly Rules the World Government

The existence of Imu changed everything about what fans knew of the World Government. While the structure of the World Government is quite complex, it was thought to be ruled by the Five Elders, the most powerful Celestial Dragons in the world who rule over Mary Geoise. In reality, Imu rules the World Government from the shadows and hands out orders from the Empty Throne, the symbolic throne that no king sits upon to allow peace between the nations of the World Government. In reality, the seat is already taken.

Imu's existence is seemingly only known to the Five Elders and not much is known about Imu or their true power. But, whoever they are, they are one of the most unsettling and mysterious characters in the series.

1 Roger Laughed on the Final Island

Laugh Tale or Raftel

One of the most impactful, yet subtle revelations in One Piece was the final island, Raftel. So much mystery has surrounded the island since its name was first mentioned. The most important island in the series by far, where the One Piece is said to be located. The legendary island has barely been mentioned or shown in the series, but during a flashback featuring Gol D. Roger, fans discovered a small truth of Raftel: its true name is Laugh Tale.

After having discovered the One Piece, Roger laughed. And so did the rest of the Roger Pirates at having found the greatest treasure in the world. They agreed to name the island Laugh Tale, which only serves to enhance the mystery of what the One Piece is and why it was so funny to the pirate king. Hopefully, fans won't have to wait too long for the answer.