Pokémon Brilliant Diamond and Shining Pearl are, largely, very faithful remakes of the original Pokémon Diamond and Pearl. But one somewhat-hidden bit of additional content might very well be teasing some lore for Pokémon Legends: Arceus.
If you recall the Canalave Library from the original games, it's full of books that relate to the myths and legends of the Sinnoh region. There are a number of tales referencing legendary Pokémon like Arceus, Uxie, Mesprit, Azelf, Giratina, Palkia, Dialga, and others. There are even a few strange stories that seem to confirm people, at least at one point, ate Pokémon, and another that implies Pokémon were once indistinguishable from humans.
For the most part, all of these texts are recreated in their original translations again in Brilliant Diamond and Shining Pearl, aside from one line in the "Sinnoh Myth" tale that appears to have been adjusted for clarity. However, there's an entirely new tale hidden on the second floor of the library that wasn't there in the original games.
Entitled "The Sea's Legend," the flavor text states that the book "was only recently discovered and its ancient letters were decoded." It reads as follows:
Once upon a time in the East Sea, there was a Pokémon known as the prince. A brave human asked Pokémon living in the sea to let them see the prince. Mantyke, Buizel, and a Quilfish with huge spikes acknowledged the human's bravery and joined them. Together, they set off in a boat over the sunset-streaked sea, sailing through the ocean gate stretched over the waves. News of this reached the ears of the prince, who went to meet the brave little party at the Seaside Hollow.
The story ends abruptly there, but it's entirely possible that this strange story — which does not appear to link to anything specific in Brilliant Diamond and Shining Pearl — is teasing something about Pokémon Legends: Arceus. For one, there's no known location in the Pokémon games thus far called the Seaside Hollow, nor does it seem to correspond to anything currently in Brilliant Diamond or Shining Pearl.
As for the "prince," it's possible this could refer to Manaphy, who in the film Pokémon Ranger and the Temple of the Sea is known as the "prince of the sea." The plot of the film involves the heroes returning a Manaphy egg to a Sea Temple, where an item called the Sea Crown is kept. Typically, anime plots don't cross over much into the main games (Pokémon Yellow aside) but this could at least hint at who this mysterious "prince" might be. While Manaphy does appear in Brilliant Diamond and Shining Pearl, it's only as a Mystery Gift and without any plot tied to it or secret locations.
It's also worth noting that the review embargo for Brilliant Diamond and Shining Pearl explicitly forbade mentioning any of the contents of the books in the Canalave Library. Given that this is the only significant change to the books from the originals, it seems that this new book was at least an important enough addition or spoiler that Game Freak wanted to keep under wraps ahead of release.
We won't know exactly what this refers to until Pokémon Legends: Arceus drops next year on January 28, though we've already heard a number of tidbits about its new "noble" Pokémon, its Monster Hunter-like world, and some creepy looking "found footage" style teases. In the meantime, Brilliant Diamond and Shining Pearl are still worthy remakes for their faithful recreation of Sinnoh and a time when Pokémon was a bit more challenging.
Rebekah Valentine is a news reporter for IGN. You can find her on Twitter @duckvalentine.