The new trailer for Pokémon Legends: Arceus has a reference to an item that was cut from Pokémon Diamond and Pearl. The item is the Azure Flute, and it was originally meant to be used to encounter the Mythical creator Pokémon Arceus. However, it was never officially distributed to players and Arceus was instead just given to players during events.
The Azure Flute in Pokémon Diamond and Pearl was originally meant to be given to players as an item during an outside event. Once the player acquired the Flute, it could be used in the Spear Pillar. The Flute would play an eerie noise. Once the music stopped, a clear stairway would appear, leading players to the Hall of Origin. It's there that the player would be able to battle Arceus and capture the creator Pokémon for their own team.
It's unclear why the Azure Flute was never distributed. Some have speculated that it too closely references religious themes. Arceus is meant to be the creator of Pokémon, yet climbing the stairway to heaven for a fight might have been a little too on the nose for Game Freak. It seems that the developers of Pokémon Legends: Arceus have a different view, as the Azure Flute may be making a comeback.
Pokémon Legends May Bring Back Diamond & Pearl's Azure Flute
A new trailer for Pokémon Legends: Arceus has been uploaded to The Official Pokémon Channel on YouTube. The player character is shown playing a purple flute, which seems to be used for calling rideable Pokémon. Although it's officially called the Celestica Flute, the noise made by this flute is identical to the sound of the Azure Flute from Pokémon Diamond and Pearl. Players have been able to hack the Azure Flute item into their game, in order to access the Hall of Origin/Arceus event. A video of the event (including the sound of the Azure Flute) can be seen on the SatoMew YouTube channel.
This might be the most obscure reference within the Pokémon series, considering the Azure Flute was never officially given out to players. It's possible that it will be important to the story of Pokémon Legends: Arceus. The fact that Arceus is the box Legendary confirms that it will have an important role to play in the story. It's possible that the event cut from Pokémon Diamond and Pearl will happen in the distant past of the Sinnoh region, and the player will end the game with a final climactic battle in the Hall of Origin.
Pokémon Legends: Arceus will be released for Nintendo Switch on January 28, 2022.
Source: The Official Pokémon YouTube Channel, SatoMew/YouTube