The Reverie (literally translated as "World Council") is a council formed by the World Government which consists of 50 of the world's leaders out of the over 170 nations affiliated with the World Government.
Every four years, kings or queens gather at Mary Geoise for a seven day conference to discuss matters that could affect the world.
As this is a meeting of leaders of nations, a full scale war could be initiated if one king simply insults another. An example is when Wapol purposely hit Nefeltari Vivi as an act of revenge against her father, Cobra, after he scolded Wapol for his selfishness. Due to Vivi's and Cobra's kindness, they did not retaliate with war, and Wapol was simply angry and left. The possibility for conflict is heightened due to the extreme range of viewpoints among the kings.
With a gathering of so many world leaders in such a "sacred" place, there are naturally some rules and regulations put in place. One such rule is that everyone, whether they be the royalty, their companions or their escorts, are to be disarmed for the duration of the Reverie.
All heads-of-states attending the Reverie are expected to make a pledge before the Empty Throne, both as a sign of allegiance to the World Government, and to symbolically state they are supporting the current "peace".
Each meeting, one of the participants acts as chairman. The chairman is chosen in rotation among all participants. During the current meeting, the chairman is KingHam Burger from the Ballywood Kingdom.
Eight years ago, participants discussed Dragon and his actions, stating that within four to five years, he would become a major threat to the World Government. This caused a conflict between Nefeltari Cobra and Wapol when Cobra scolded Wapol for not taking the threat seriously.
The queen of the Ryugu Kingdom, Otohime, had worked on gathering signatures from her subjects to petition the World Government to relocate Fishman Island to the surface as a sign of furthering the peaceful relationship between Fishman Island's nativeraces and the humans that comprise the majority of the surface population. Even after her assassination, Otohime's family had worked to continue and fulfill her objective for years and attended the current Reverie to finally make their request.
Despite his disagreement with Sakazuki, AdmiralFujitora went to Mary Geoise and encountered his colleague Ryokugyu. While they ate, they talk about Fujitora's travels and Dr. Vegapunk's new creation that Fujitora believed would make the Shichibukai system obsolete, which he planned to bring up to the Reverie participants. Later, Pell told Vivi that Fujitora was in a meeting with Nefeltari Cobra and Riku Dold III.
200 years ago, Ryugu Kingdom joined the World Government, and its king was granted a place on the Reverie.
16 years ago, Queen Otohime, in an effort to get fishmen and merfolk to grow closer to humans, made a proposal to relocate Ryugu Kingdom to the surface. She wanted to present this wish at the Reverie that year, and asked her kingdom's citizens for signatures.
15 years ago, King Neptune stated that he would not be allowed to attend the next Reverie due to the recent incident of Fisher Tiger raiding Mary Geoise and liberating slaves, which caused Fishman Island's standing to fall.
10 years ago, Otohime went to Mary Geoise and returned with an official letter from a World Noble, supporting her cause to relocate Ryugu Kingdom. She stated that the plan could be realistically put into action if enough signatures are collected by the next Reverie.
8 years ago, a Reverie was held, with the participants including Thalassa Lucas, Nefeltari Cobra and Wapol. During the meeting, Lucas brought up the Revolutionary Dragon, labeling his ideologies "dangerous" and stating that he would become a great threat to the World Government in 4-5 years. Wapol disregarded this as not concerning his country, which prompted Cobra to scold him for his irresponsibility. After the meeting Wapol came across Cobra's daughter Vivi and purposefully hit her as revenge against Cobra. Vivi, however, simply apologized in order to avoid conflict between their countries.
Despite no longer ruling any land, the Vinsmoke Family, as the ruling family of the maritime Germa Kingdom, retain the status and the privileges of royalty, including the right to attend Reverie. However, Vinsmoke Judge expects the family's activities will imminently lead the World Government to strip them of this right.