Pyrex

Pyrex is the het ship between Rex and Pyra from the Xenoblade Chronicles fandom.

Canon
Both Rex and Pyra share the same life force, as Pyra's core was placed in Rex's chest. She acts as a support throughout the series. Both want to reach Elysium, Rex so he can stop wars and ask for enough land so everyone can live in peace, and Pyra for a similar reason.

Xenoblade Chronicles 2
Shortly after Rex is killed by Jin, Rex then finds himself in a quiet field, with a girl standing next to a single tree. Rex realizes the girl is a Blade, and she introduces herself as Pyra. She then affirms the legends of Elysium and reveals that they are in Pyra's memory. She asks Rex to bring her to Elysium and in return, she would bring him back to life. Rex agrees and touches the core crystal on her chest and is suddenly resurrected with a green crystal on his chest like hers.

Rex and Pyra reawaken and charges at Malos, but they are both easily overpowered by Malos. A girl, Nia, tries to stop him but gets pushed off the ship by him, Azurda then comes in and saves Nia, and both Rex and Pyra escape.

Shortly after, Rex and Pyra go to Torigoth city, where Nia is kidnapped by Lady Mòrag and rescue her. They then fight Mòrag and Brighid, however, they are no match for them. When Mòrag tries to take Pyra away, Rex states that they treat her as some kind of machine or tool, but she is a living and breathing being with feelings. The two then attack the water tank and exploit the fire blade's weakness and run away. Later at a campfire, Rex and Pyra relax and help to fix each other’s wounds. Pyra comments that the fire is beautiful and Rex believes that because she made it. Pyra says that’s what she does and blows the fire in the air, smiling at Rex.

Xenoblade Chronicles 3
While Rex and Pyra didn't returned at the present time of the game, they reappeared in a picture at the end when Nia reunites with Poppi, at there we see an adult Rex with the rest of the party, and below of him we can see Mythra, Pyra and Nia with a baby each, this reveals that Rex, after the second game, married all three (or four if Pneuma is included) and had three children with each.

Super Smash Bros. Ultimate
After the events of Xenoblade Chronicles 2, Rex finds himself quite depressed over Pyra's apparent disappearance. Since she "disappeared" without a trace, Rex asks all of his friends, but they all tell him that they haven't seen where Pyra is. After this, Rex becomes even more depressed and to vent his sorrows, he goes to the Ancient Ship where he met her for the first time to remember the first moments. Rex steels himself, however, and swears to himself that he will find Pyra, no matter what it takes.

After moments of searching, Rex heads to another unusual otherworldly dimension he hasn't seen before in his world, where he finally finds Pyra. Excited, Rex walks over to her, but Pyra starts to express her sorry that she didn't tell him something earlier, which Rex stops. Much to Rex's surprise, Pyra received an invitation letter to join the Super Smash Bros. Ultimate roster and both are in the Final Destination stage. When Pyra reveals the Smash letter to him, Rex is even more surprised as Rex thought he would be the one to join. Rex is surprised that even outside of his world Pyra can do the same attacks as in his world, including switching with Mythra and their encounter with Shulk in Smash.

In gameplay, Rex appears in Pyra's taunts and victory poses, as well as her Final Smash, Burning Sword. If the DLC is purchased, a Pyra puppet replaces Lucina to assist the Shulk puppet, who possesses Rex's spirit to combat the player character.

Moments

 * When Rex was climbing a mountain, he clutches his chest in pain, knowing that Pyra was feeling it as well.
 * Pyra thanks Nia for protecting and healing Rex.
 * When Rex would get hurt, they would both stitch each other’s wounds up as since they share the same life force, they both obtain identical wounds.
 * After their final battle with Morag, Pyra and Rex banter affectionately.
 * Rex's anguish when Pyra is captured by Torna.
 * Pyra's conversation with Corrine.
 * Rex's conversation with his deceased parents.
 * Rex accidentally calls Pyra pretty before backpedaling. Pyra smiles in response.
 * Pyra's expression when Rex says Morag won't take her.
 * Rex shocked when Pyra enters Super Smash Bros. Ultimate.

Fanon
Shipping between these two is very common and has been around since the game came. It is one of the most popular ships in the Xenoblade fandom, it’s also considered a rival-ship to Rexia or Mythrex. Both Mythrex and Pyrex is often argued over which is more likely to be canon. But as Xenoblade Chronicles confirmed, Rex married both of them, making both canon.

Fandom
FAN FICTION
 * Pyra x Rex on Doctruynhot
 * Pyra/Rex tag on Fanfiction.net
 * Pyra/Rex tag on Fanfiction.net