Fade in to the base of a tapestry design not unlike those in Hammerlocke's vault. Gentle flames illuminate the scene, flickering from some location behind the viewer. The camera pans upward slowly to reveal more of the design, and a narration appears on the bottom of the screen.
"Once upon a time, not so long ago, the region of Galar met with a calamity only spoken of in legends."
(Voice acting for the narration is optional due to circumstances. If done, it would be the voice of a young woman with some kind of British accent, implied to be Sonia.)
As the camera pans upward, this tapestry is shown to be depicting the Wild Area during the Second Darkest Day. Heraldic depictions of a blackened sky and Dynamax-sized Pokémon wreaking havoc are displayed prominently.
The camera fades to black, then back in to show a different tapestry. This one depicts a forest clearing shrouded in mist.
"In Galar's time of need, a pair of young champions braved the odds, retrieving the regalia of two long-forgotten heroes...and reviving them once more."
As the camera pans up, it becomes clear that the tapestry is depicting the lakeside shrine deep within the Slumbering Weald. Two silhouettes of adolescent humans are seen presenting a sword and shield to two larger, distinctly wolf-shaped silhouettes. They look on with curious yet gentle expressions, to highlight their heroic nature despite their bestial appearance.
The camera fades out again, to a third tapestry. This one depicting the crumbling ramparts of a castle assailed by a strange, violet energy.
"Joining forces, the four heroes faced the calamity at its source, defeating it once again just as hundreds of years ago. "
As the camera pans, it doesn't take long to realize this tapestry is depicting the final battle against Eternatus' true form. The two humans are still in silhouette (since the player character has no canon appearance or gender), but now Zacian and Zamazenta are shown in full, their prowess with sword and shield on display doing battle against the otherworldly abomination.
"For now, Galar was at peace once more..."
The camera fades to black, then shows one more tapestry. This one has enough on the bottom to show Zacian and Zamazenta on a high cliff overlooking a wooded land, their gazes focused on the horizon as the rays of the evening sun beam down from above.
"But for the heroes of legend...they could not rest just yet. For far away in time and space, another realm was in need of saving."
As the camera pans upward, it becomes clear that the "sun" overhead...is actually a Smash Ball. The camera stops with the iconic symbol hanging overhead and Zacian and Zamazenta in view at its base.
"Wait a minute...I don't recall this part of the story."
Fade to black.
---
Cut to a bird's eye view of the World of Light during Dharkon's assault. The camera quickly passes the clearing where Hero's trailer began, then the ruined mountaintop where it finished, revealing this scene takes place some time afterward. Beyond the summit lies another ancient ruin, the remains of a village built amidst a mountain pass. Sounds of combat ring out.
Cut to ground level, showing Link and the Luminary in battle against Dharkon's puppet legion. They exchange a few blows with the puppet fighters, then two more enter the fray: Marth and Meta Knight, freshly liberated from the dark god's thrall. The heroes have made progress since we last saw them, but now they're becoming overwhelmed again.
The puppet fighters surround them and prepare to strike, but then...
A piercing howl rings out, staggering them. That is, a very recognizable three note howl, harmonized in two voices.
The camera backs up and looks overhead, as two familiar figures now stand on a cliff face overlooking the scene. At first they are draped in shadow, but not for long, as shimmering energy washes over them, forming their weapons and armor from thin air.
Now ready to enter the fray in this new world, Zacian and Zamazenta stand ready. Depending on who was chosen to be the newcomer, either--or both--step forward.
Cue splash art.
Cue gameplay.