Zacian and Zamazenta

Zacian and Zamazenta, also know as The Heroes of Many Battles, are the Mascot Legendaries of Pokémon Sword and Shield. The are the guardians of the Galar Region, who according to the legends protect Galar from outside threats before they faded into myths.

Background
20,000 years ago, a meteorite containing the Pokémon Eternatus crash landed on the Galar region. Eternatus nearly destroyed the Galar region absorbing all the energy on it's path, until it was defeated by Zacian and Zamazenta, who used their powerful sword and shield to fend off the dangerous alien. The two Legendary Pokémon suffered grave injuries during the battle, including both of them missing a piece of their ears and their armors completely breaking down leaving them in a significantly weakened state. After the battle Zacian and Zamazenta retreated to the Slumbering Wield to rest. The sword and shield that Zacian and Zamazenta were left in an altar next to their resting place. It is implied that Zacian and Zamazenta passed away while their spirits remained in the altar watching their old weaponry.

Over the generations, the battle of Zacian and Zamazenta faded into myths while Eternatus came to be known as "The Darkest Day in Galar". The energy that Eternatus radiated during that battle was harnessed by the people of Galar, leading to the discovery of Dynamaxing. Over time the myth of Zacian and Zamazenta was continously misconstructed, eventually the two Pokémon were forgotten from the myth and instead it was told that a human "hero" defeated "The Darkest Day" with a sword and a shield, only a statue depicting Zacian and Zamazenta remained in the area that would eventually become the town of Stow-on-Side, however the statue was buried behind a mural depicting the incorrect myth. The Slumbering Wield became a forbidden place for humans to venture into, with a dense fog produced by the spirits of Zacian and Zamazenta scaring off visitors. It was rumored that "an extremely dangerous Pokémon" resided within the Slumbering Wield, further discouraging people from entering the forest.

The existence of Zacian and Zamazenta was all but forgotten as the Slumbering Wield was considered too dangerous for anyone to go into.

Pokémon Sword and Shield
In the present day, two trainers named Victor/Gloria (depending on the player's gender) and Hop ventured into the Slumbering Wield looking for a stray Wooloo that sneaked into the forest. The two trainers soon got lost in the dense fog and stumbled into the spirit of Zacian/Zamazenta (depending on the version of the game). Victor/Gloria attempted to battle Zacian/Zamazenta but none of their attacks could harm it while the Legendary Pokémon made the fog thicker until the two trainers passed out. Hop's older brother Leon found the two unconscious and helped them exist the forest after he found the missing Wooloo.

The following day Hop and Victor/Gloria told Professor Magnolia about the incident, the professor instructed her grand daughter Sonia to investigate the myths of Galar to find out more. Throughout Victor/Gloria and Hop's journeys across the region they would frequently meet up with Sonia as she slowly discovered more about the legend of the "Darkest Day" and realized that the myths as they were told in modern times were incorrect after finding the lost statue of Zacian and Zamazenta.

During the finals of the League Championship, the Chairman Rose revived Eternatus in an attempt to harness it's energy to prevent a future energy crisis from impacting the Galar region, however his organization the Macro Cosmos was widely unprepared to handle Eternatus and it soon escaped. Rose interrupted the finals to announce that Eternatus was once again attempting to destroy Galar. Hop suggested going back to the Slumbering Wield and find Zacian and Zamazenta knowing that they defeated Eternatus before.

Hop and Victor/Gloria found the spirits of Zacian and Zamazenta once again but in ther weakened form they were unable to do anyhting. Instead, the two trainers took the sword and shield that the Legendary Pokémon once wielded, which were now completely rusted out. Hop and Victor/Gloria attempted to face Eternatus but were vastly outmatched by it's "Eternamax" form. At that moment Zacian and Zamazenta were revived as well, the two rushed to the battlefield and absorbed the energy from the rusted sword and shield to regain their fully revitalized armored forms. Zacian, Zamazenta, Hop, and Victor/Gloria all joined forces together to take down Eternatus once more and Victor/Gloria caught it. With the battle over, Zacian and Zamazenta returned to the slumbering wield once more.

Post-Game
Not long after the battle against Eternatus and Victor/Gloria became the new champion, Sonia published a book detailing the true legend of Zacian and Zamazenta. This book angered Swordward and Shieldbert, two descendants of the ancient Galarian royal family who believed themselves to be the real heroes of Galar. The siblings plotted to steal the Rusted Sword and Shield and large amount of Dynamax energy in order to create a rampage of Dynamaxed out of control Pokemon to cause chaos and blame it on Zacian and Zamazenta by also corrupting them with forced Dynamax energy.

Victor/Gloria, Hop, and Piers all joined together to thwart Swordward and Shieldbert's schemes, which ended with Victor/Gloria and Hop catching both Zacian and Zamazenta after bonding with them. Which of the two Legendary Pokémon Victor/Gloria catches depends on the version of the game.