The Fairy Tail series is filled with mysterious occurrences and secretive schemes, and the 400 Year Plan is one such overarching scheme. Similar to other aspects, the 400 Year Plan remained hidden until later in the series when it was finally disclosed to the viewers. This shocking development connected various events and allowed the audience to make sense of the story.
The unveiling of the 400 Year Plan provides an explanation for the presence of Dragon Slayers in the current timeline, even though dragons have been extinct for centuries. It also serves to establish a deep connection between Lucy and Natsu that spans centuries. Zeref's involvement in the plan adds complexity to his character, as his motivation for this mission is to save humanity.
The Events That Led to the Plan
During the time when Dragons existed, about 400 years before the series, Zeref encountered Igneel, a peaceful Dragon who believed in the harmony between humans and Dragons. They developed a close relationship and Igneel agreed to train Natsu in Dragon Slayer Magic. However, this happened during Acnologia's destructive rampage, making him a grave threat to both humans and Dragons.
Knowing that teaching humans Dragon Slayer Magic wouldn't be enough to defeat Acnologia, Zeref sought another solution. Fortunately, he met Anna Heartfilia, a talented mage with a rare skill in Celestial Spirit Magic. Together with the peaceful Dragons and Anna, Zeref devised a daring plan to use Celestial Spirit Magic to open the Eclipse Gate, a device that allows travel to the future. Through the Eclipse Gate, five chosen Dragon Slayers would be transported to the future, with their foster Dragons sealed within them.
The 400 Years Plan
Zeref's plan, centered around time-travel, initially appeared confusing and illogical. However, due to the imminent threat of annihilation from Acnologia, the other two parties had no choice but to agree. Five Dragons, who were pacifists, were sealed within their foster children - Natsu, Wendy, Gajeel, Rogue, and Sting. The purpose was to bring these Dragons to a time period abundant in Ethernano, allowing them to heal their wounded souls and regain their strength.
To open the Eclipse Gate, someone in the future had to utilize Celestial Spirit Magic to create a connection between the two timelines. This responsibility fell upon the descendants of Anna, and the Heartfilia Clan faithfully carried out this task by passing down the secret of the 400 Year Plan. Finally, 400 years later, Layla Heartfilia successfully opened the Eclipse Gate on July 7th, X777, enabling the chosen Dragon Slayers and Anna Heartfilia to travel to the future. Once the plan was accomplished, Anna took it upon herself to locate the scattered Dragon Slayers while the pacifist Dragons continued to remain sealed within their foster children, patiently awaiting the opportune moment to reveal themselves.
The Aftermath of the 400 Year Plan
However, the consequences of the plan brought about dire circumstances for several individuals involved. The Dragon Slayers were scattered and lost in the altered timeline, completely oblivious to the unfolding events, which led them to believe their foster parents had forsaken them. Layla Heartfilia was also greatly affected as she possessed only 11 of the 12 Zodiac Keys when it came time to open the Eclipse Gate. As she was compelled to utilize her own life force to compensate for the missing key, her physical well-being deteriorated significantly, resulting in the development of an incurable ailment.The 400 Year Plan achieved success when the Eclipse Gate was opened, providing an opportunity for the peaceful Dragons to fight for their fallen comrades. Layla, Anna, and Toma E. Fiore, the ruler of the Kingdom of Fiore, held discussions about the recent events and the future course of action. Anna made the decision to locate the missing Dragon Slayers and support them in their mission. Meanwhile, Layla requested Toma E. Fiore to destroy the Eclipse Gate. However, he refused, citing its usage during the Grand Magic Games. Unfortunately, Layla's health eventually deteriorated due to the Magic Deficiency Disease caused by using her own life force to open the Eclipse Gate.
In the Tartaros arc, Igneel and the other Dragons who advocated for peace finally appeared and confronted the powerful Dragon King, Acnologia. Although they were unable to defeat him, their presence managed to discourage him and provide a valuable opportunity for the Dragon Slayers. Before their souls vanished, the Dragons briefly elucidated certain events, offering a sense of closure to the clueless Dragon Slayers.