Author's Note: This too, was a part of my unfinished episode 9 fanfic. I find that it works in canon as well.
Rey says, "Leia, I have something for you."
Leia says, "What?"
Rey answers, "The Skywalker Lightsaber. I fixed it but the person who really should have it is you. You are the last Skywalker."
Rey hands it to Leia. When Leia first touches it, she hears a female voice say, "Master Yoda was worried that you hadn't reported in, and he couldn't reach you, so he sent me with a message." Leia sees a city on Christophsis. She guesses that the time is during the Clone Wars. She sees Obi-Wan and a younger man standing next to each other. Turning around, she sees a small Togruta girl.
A voice she recognizes as Obi-Wan's says, "Sent you? So, where's the cruiser? Where are our reinforcements? Our support?"
Ahsoka says, "The ship dropped me off. Master Yoda wants you to return to the Temple right away. There's an emergency."
A voice she recognizes as Anakin's says, "Funny, we've got one of those too, in case you haven't noticed." He paused, "Are you telling me they never got our signals asking for help?"
Ahsoka says, "I don't think they did. Perhaps we can relay a message via the cruiser that brought me."
Anakin says, "And who are you?"
Ahsoka says, "I'm Padawan Ahsoka Tano."
Leia realizes that the young girl is Ahsoka Tano. She must have grown a lot by the time she became Fulcrum.
Obi-Wan says, "Ah, my new apprentice." He bowed and says, "Nothing like being thrown in at the deep end."
Ahsoka says, "No, Master, I'm not your assigned Padawan." She turns to Anakin and bows. "I'm yours, Master Skywalker."
That world fades to black. She sees a fiery world and recognizes it as Mustafar. She sees Anakin, who had just fallen to the dark side laying in lava. She sees the saber laying on the ground nearby. All she hears are Anakin, now Darth Vader's screams. She sees Obi-Wan pick up the saber and walk away.
She sees Mustafar fade to black and sees Rey on Ahch-To holding a lightsaber for an instant. She then sees Rey fixing the saber in Luke's hut on Ahch-To. All is silent. She then sees herself holding the saber and using it somewhere. Was that Ajeen Koss, the world where Luke trained her? She sees Han using it to cut open a tauntaun on Hoth to save Luke.
She then hears a message in the Force. The Force says to her, "This was your father's crystal journey. The Crystal Journey was something Padawans did in the old Jedi Order. It was a Padawan's final test before becoming a Knight. This is before you and Luke were born. Your father was a Padawan in this scene and was looking for the crystal that bonded to him. This is on Ilum, the world that was hollowed out to create Starkiller Base. This was an old ritual among the Jedi Order. Your ritual you will use in the New Jedi Order is using the Force to create a kyber crystal. Here is where he found the crystal that would change the galaxy forever. "It is dark. Leia realizes this is in a cave on Ilum. She sees a glowing blue crystal up high overhead. It is calling through the living Force, "Anakin. Anakin. Anakin." It keeps calling for him again and again. Finally, Leia hears footsteps coming into the chamber of the cave. They are Anakin's. He hears and sees the crystal wants to bond with him. Leia sees him turn on a headlamp and look at the crystal. He makes a big Force-assisted leap and grabs the crystal. He turns off the headlamp and walks out of the chamber. The Force says to Leia, "You, too are a Skywalker. A member of the greatest family in the Force. Become a great Jedi."
The world around Leia fades back to normal.
Rey says, "Did you have a Force Vision?"
Leia says, "Yes, I did. It first was of Ahsoka Tano on Christophsis, after getting dropped off as Anakin's Padawan. Then it was of Anakin as Vader on Mustafar, with Obi-Wan picking the saber up. Then I saw you holding it on Ahch-To for an instant, then you fixing it. Then it was Han cutting open a tauntaun on Hoth to save Luke. Then-" Rey stopped her.
Rey says, "Huh. Where in the galaxy is Hoth?"
Leia replies, "Hoth is in the Suantas-Kashhak Sector. It was home to a Rebellion base until it got discovered, around the time Luke lost his hand on Bespin. It is a frozen world. The biggest native creatures are Wampas. They don't coexist well with humans. I think it wouldn't be used for a Resistance base, as I know from experience that the native wildlife don't coexist well with humans. The last part of the vision I saw was Anakin's crystal journey. That is where he found the crystal that would change the future of the galaxy. It was on the world that became Starkiller Base. The last Gathering, the ceremony where Republic Jedi got their kyber crystals was probably 18 or 19BBY. After that, there was a "Shoot on Sight" order for troopers to kill Jedi. "