Having Koei Tecmo create a prequel to The Legend of Zelda: Breath of the Wild in the style of its Dynasty Warriors series is a stroke of genius in many ways. Hyrule Warriors: Age of Calamity promises to fill the gaps in Link's memories of the war that takes place 100 years prior to Breath of the Wild, and it makes perfect sense to set that in a hack-and-slash style where Link, Zelda, and the Champions of Hyrule can prove their status as legends by defeating thousands of opponents with ease. However, this premise comes with its share of potential pitfalls.
Every prequel is ultimately beholden to one rule: Maintain the status quo. Prequels usually offer a great way to flesh out how a character acted or thought leading up to specific events, but they cannot change those events without larger ramifications. For example, Star Wars Episodes 1 through 3 set up the fall of the Republic and rise of Palpatine's Empire, yet they could only do so much with the characters like Anakin because everything needed to build to his Darth Vader transformation before Episode 4. As great as Age of Calamity may be, both its story and gameplay could suffer due to these constraints.
Effects on Story
As soon as Hyrule Warriors: Age of Calamity was announced, many people jumped to the same conclusion: The Champions will all be dead by the end of the main campaign. That is how the war ended based on stories in Breath of the Wild. In fact, a major part of Link's journey is freeing their spirits so they can help to fire the Divine Beasts at Calamity Ganon in Hyrule Castle. These deaths, and many other plot points, are set in stone and limit how much the cast of playable fighters will ultimately be able to accomplish.
The character who may suffer the most in this regard is Mipha. Based on story beats established in Breath of the Wild, the Zora Princess arguably has the most potential outside of simply being a powerful warrior and icon for her people. Players meet her immediate family, rather than her descendants, because of their long life spans. Thus, Age of Calamity has the opportunity for players to meet Mipha's established relatives like Sidon in the past. She is also established to have an unspoken, and perhaps unrequited crush on Link, meaning there's ample opportunities to see them interact in the past and help justify those feelings.
However, this ironically makes Mipha a more rigid character with less personal agency. While she can choose where to fight what armies, she cannot choose to tell Link about her feelings; nor can the game introduce as many new Zora characters without it being odd they aren't around in the future. This may frustrate some players who are invested in learning more about the Champions that Breath of the Wild did not establish, as Mipha is somewhat pigeonholed by the status quo. Characters like the Goron Champion Daruk, on the other hand, has more nebulous relationships and interests to build upon in the prequel.
Fire Emblem Warriors, a previous Nintendo/Koei Tecmo venture, avoids this problem by plucking characters out of their original worlds for a separate adventure. Marth and Chrom could express varying interests and form new bonds because the entire adventure was essentially a "filler arc" in their lives. The same can be said for Intelligent System's mobile game Fire Emblem Heroes, which frequently pairs up disparate characters due to similar interests. The same can't be said for Age of Calamity because it is a direct prequel.
Effects on Gameplay
One major strength of the original Hyrule Warriors is that it was not necessarily tied to any canon, so it could go wild with abilities. Innocuous characters like Agatha from Twilight Princess could kill hundreds of monsters in single attacks, and pulling from a range of source materials led to fun, inconsequential references like Link attacking with the moon from Majora's Mask. The initial trailer for Age of Calamity shows its characters will stick with this Dynasty Warriors tradition of bombastic attacks and solo units slaying armies, but this opens up a strange grey area.
The ultimate problem with this kind of power fantasy hack-and-slash gameplay being applied to the prequel for a game in a completely different genre is that it brings each individual's strength into question. For example, it makes one wonder how characters like Mipha, Daruk, Urbosa, and Revali can effortlessly kill thousands of opponents with epic, flashy maneuvers, and then still be too weak to defeat fringe vestiges of Ganon in the Divine Beasts. By extension, if Calamity Ganon is truly that unimaginably powerful, one must wonder how Link defeats it in Breath of the Wild after presumably being so downgraded during his 100-year slumber that he now focuses on slower, single-enemy combat.
An obvious answer to this question is that it's a video game, and players should apply enough suspension of disbelief to know Link and his companions were not literally downgraded. This is just the stark contrast between a hack-and-slash title and a slow, exploration-heavy adventure game. Yet, if Nintendo wants to position Age of Calamity as official canon, it's going to be hard for fans to completely turn their brains off when presented with an opportunity to connect the dots like never before.
All of this talk about character agency might not matter as much if Age of Calamity is more of an interquel, or a framed story focused on Link being given the context for the war with Calamity Ganon. If that is the case, it may not be as important to create satisfying character narratives or keep power levels strictly accurate. After all, it would just be an over-embellished yarn being spun.
However, Age of Calamity is the perfect opportunity for Nintendo to give audiences more reason to care about the characters it established in Breath of the Wild. It would behoove them to really do so before moving into the official sequel, whenever that may come out.
Hyrule Warriors: Age of Calamity launches November 20, 2020, exclusively for Nintendo Switch.