Pokémon Brilliant Diamond & Shining Pearl were released on November 19, just two months before the upcoming January 2022 release of Pokémon Legends: Arceus, and they contain several hints at what players may experience on their next journey. These games are more connected than any other Pokémon games due to being set in the same region - the main difference is that they're set in different time periods and therefore have different region names. Set in the past, Legends' Hisui region will feature new Regional Variants and evolutions not present in modern-day Sinnoh, as well as a slew of new characters.
In fact, the characters in each time period are some of the first hints connecting Legends to Brilliant Diamond and Shining Pearl. The player characters in Legends look incredibly similar to Dawn and Lucas in BDSP, indicating that the latter could be descendants of Akari and Rei, respectively. At the same time, many other apparent ancestors appear in pre-release footage of Legends. Commander Kamado, the leader of the Galaxy Team, is confirmed to be Professor Rowan's ancestor, but other characters' connections aren't confirmed. These include Legends: Arceus' Arezu looking like BDSP's Mars, Cyllene looking like BDSP's Cyrus, and Lian even appearing like Unova's Clay. Interestingly, these characters' BDSP personas might hint at their ancestors' traits, too.
In addition to parallel character features, Pokémon Brilliant Diamond and Shining Pearl hints at Legends: Arceus through various Easter Eggs. The Sinnoh region's central plot around Team Galactic and Dialga or Palkia depending on one's version remains unchanged since the original Diamond and Pearl, so the remakes' story beats don't hint at Legends. Still, several Easter Eggs around the region act as potential foreshadowing for what fans will experience in Hisui. These hints include a new book at the Canalave Library, a dark Giratina, and Spear Pillar's detailed graphics. Petting Pokémon in BDSP might even hint at cute interactivity between trainer and Pokémon in Legends: Arceus.
Hisuian Qwuilfish May Feature In Pokémon Legends: Arceus
A now well-known Easter Egg can be found in a new book in the Canalave Library. This book, which wasn't in the original Diamond and Pearl, tells the tale of a prince who lives in the East Sea. The East Sea, while not a specific location in Sinnoh, isn't news. Mt. Coronet divides the region in half, and the Gastrodon on either side are known as East Sea Gastrodon or West Sea Gastrodon. Gastrodon's Pokédex entry may even hint at a new evolution for the two-stage evolution line. However, a prince who lives in the sea can seemingly only refer to the Mythical Pokémon Manaphy in BDSP.
Manaphy is known as the prince of the sea in Pokémon lore, including in the film Pokémon Ranger and the Temple of the Sea that features them. Because of this book seemingly describing Manaphy, Legends could see players taking on a research quest covering this Mythical species. There's already precedent for Mythical research, too. Pokémon's official website already announced that Legends: Arceus' postgame will feature a research quest to find and learn more about Shaymin, the Mythical Gratitude Pokémon. Players can receive a Manaphy Egg in BDSP simply by connecting to the internet, so incorporating Manaphy into a story would be nice. It also breeds Phione, which seems like something important to research.
At the same time, this Canalave Library book that mentions the East Sea's prince lists a number of Pokémon that inhabit the area, and who could appear in Legends: Arceus. Among them is a Qwilfish who's described as having big spikes, which sounds like it's a Regional Variant Pokémon that's harder and spikier than the Qwilfish with which players are more familiar. No other listed Pokémon is described with different traits in the book, so singling out Qwilfish without hinting at a new, potentially Steel-type form would be strange.
Giratina Could Play A Pivotal Role In Legends: Arceus' Story
In Pokémon Brilliant Diamond and Shining Pearl, Giratina is located in Turnback Cave as in Diamond and Pearl and not in the Distortion World as was the case in Pokémon Platinum. However, as an homage to Platinum, players can enter the Distortion Room at Ramanas Park after catching Giratina in BDSP. Here, they can obtain the Griseous Orb by defeating a dark, shadowy Giratina. This 'mon can't be caught and exists solely as a boss guarding the Griseous Orb.
This dark Giratina has never appeared before in the Pokémon franchise, but it might hint at Giratina playing a pivotal role in Legends: Arceus. This is in part because not much is currently known about the game's story outside of players traveling to research the Pokémon of the Hisui region. Giratina is a sinister Pokémon, and its dark counterpart in BDSP could seemingly indicate that it has a "darkness" in Legends, whether a metaphor for Giratina's inherent darkness or simply that this dark Giratina itself plays a villainous role in the game.
Interestingly, Giratina is the central legendary Pokémon in Platinum, and Team Galactic's chief scientist who engineers a way to get to the Distortion World to capture it, Charon, is missing in BDSP despite an apparent relative appearing in Arceus' pre-release footage. This may only be because Charon wasn't in the original Diamond and Pearl, but it seems suspicious that a man resembling Charon can be seen working in Jubilife Village in Legends: Arceus' trailers after not in the Diamond and Pearl remakes. This could potentially hint at something happening to his Legends' ancestor, causing a disruption to his family line.
Arceus Could Be Caught In BDSP Through Legends: Arceus
When players reach the climax of Pokémon Brilliant Diamond and Shining Pearl's plot, they're required to hike to the top of Mount Coronet to reach a sacred location called Spear Pillar. Here, there's a mural on the ground depicting a flute, just as in the original Diamond and Pearl, though it's much more defined in these remakes. This flute is the Azure Flute, which can summon Arceus if used while the player is standing on this mural. However, the Azure Flute is an event item that was never released outside of Japan during the original games' lifespan.
In BDSP, the mural is clearer than ever, and it's possible that it could be used again at some point in the future. Interestingly, Legends: Arceus' trailers show the player characters using a flute of the same shape and size in Hisui. This leads to the potential for players to receive the flute and access Arceus in BDSP if they have Legends: Arceus save data on their Switch, just as they can receive Jirachi if they have Sword and Shield save data or Mew if they've previously played Let's Go, Pikachu! or Let's Go, Eevee! There's a precedent for save data rewards, meaning there's a strong possibility the same could happen with Legends: Arceus.
Ultimately, Pokémon Brilliant Diamond and Shining Pearl don't hint at Legends: Arceus as much as they could due to how faithful they are to the original games. However, the small changes made have provided some insightful Easter Eggs, and Legends: Arceus already looks to be reshaping Pokémon lore in interesting ways as well. Lian's inclusion as an ancestor of Clay is smart because of their status as an immigrant in Unova, and it points toward Unova being the next generation to be remade now that Sinnoh has been given the current gen treatment. The staggering number of Unovan Pokémon receiving Regional Variants makes this just as interesting, so perhaps Legends: Arceus will have more Easter Eggs than Pokémon Brilliant Diamond & Shining Pearl this way.