Hiding in my Skin, Broken from Within

Chapter 20: Into the Light

So, Protective Dad Bowser may or may not have been inspired by Barret from Final Fantasy VII, haha (why doesn't FF7 even have so much as Spirits? Not even an Assist Trophy while Street Fighter and Bayonetta do. that's a real crime.) Also, bonus points to whomever spots the Castlevania: Symphony of the Night reference.

Chapter namesake - Into the Light from the Splatoon 2 Octo Expansion OST. (Team Chaos won, whoooo!)

As for the Rex part - Shulk and Fiora's journey with Rex on Alrest (them being DLC Blades) takes place after Shulk gets the Monado but before the Colony 9 invasion, as Fiora's in her Hom form there and not her late game cyborg form. As for Elma, it's explained in Xenoblade 2 that the Nopon trader gave her that VR thingy that transports her mind to Alrest or something and that time passes faster on Alrest than on Mira (and possibly on the Bionis/Mechonis as well), so her trips to Alrest can (and here, have) take(n) place during X's story.

Hiding in my Skin, Broken from Within

Chapter 20 - Into the Light

As Lucina and Captain Falcon entered the portal into the pocket dimension, they were greeted by Snake, Samus, Shulk, and everyone else as they stood on a stone bridge dividing two sections of land - the land to the north an expansive desert covered in a thick purple mist, and the land to the south a foggy forest.

"You guys... all of you have been waiting for us?" Falcon asked Shulk.

"Of course," Shulk reassured him. "I know the general location of each fighter thanks to my visions. Unfortunately, we can't go north just yet, because that thick purple mist severely limits visibility. According to my visions, the Master Sword due south can clear it, but it's blocked by a boulder and I have no idea how to clear it." Turning to Bowser, he tried to console the King of the Koopas, "Sorry, Bowser... I promise, you'll be able to save your children soon."

"Okay..." Bowser mumbled sadly before suddenly shouting, "DON'T WORRY, MY KIDS! PAPA'S COMIN'!"

"Heh..." Looking down, Shulk anxiously murmured, "Please wait for me too, Fiora..."

"So... what now, Shulk?" Lucina asked the wielder of the Monado.

"I guess all we can do for now is explore the region due south," Shulk answered her. "I think we should check out the forest first. According to my visions, Young Link and Chrom are there..."

"Father..." Lucina murmured. Placing her right hand on her daughter's shoulder in a comforting gesture, Robyn reassured her, "Let's save him together, sweetie."

"Yes..."

"Guess I'll try to find Young Link then," the Captain said.

"I'll come with you, Captain," Link volunteered. "He's another one of my incarnations, and I feel somewhat responsible for his and Toon Link's safety."

"Say whaaaat?!" Toon Link announced in surprise, alerting the other two to his presence. "There's ANOTHER me?! How many versions of me are there, anyway?"

Chuckling nervously, Link told his younger, more cartoon-like incarnation, "If you're referring to Smash... it's just me, you, and Young Link."

"How come I didn't know? I wanna meet him!" Toon Link jumped up and down with childlike excitement.

"I'll take you to him," Link said. "He's been absent since the second tournament, but Master Hand brought him back after so long." Holding his hand to his chin quizzically, he mused, "Which... I wonder why he decided to go the extra mile to bring all of us back in the first place..."