After Darth Malgus' initial attack (on the Jedi Academy of Yavin 4), those who escaped the carnage retreated to Coruscant, where they reported the situation to the Galactic Republic. Almost immediately, Han and Leia mobilized the Republic military to stand against Malgus. And once the Jedi Council heard about it, they knew that once more that it was up to them to lead the Republic army, as they did during the Clone Wars and Snoke's campaign.
Across the galaxy, Republic troops and Jedi Knights were dispatched to multiple planets to aid their planetary militias. However, as Luke went to war, he left Rey, Chris, and Destin at the Jedi Temple on Coruscant for their safety. Normally, he believed in 'learning by doing', but he didn't want to risk losing his son the way he lost his wife. Chris hadn't even truly recovered from losing his mom anymore than his grandfather once did years ago. Destin, however, was willing to do what would benefit the galaxy in these times of turmoil. He didn't know how, but he figured the secret to defeating Malgus and Zaro lied in solving the secret left behind by his ancestor.
Meanwhile, Luke has travel to the mine-world of Crait, where Malgus and Zaro sought to rob the planet of its wealthy resources. A battalion of giant, 4-legged walkers stalked the terrain towards a mining facility the militia and Republic troops were using as a base of operations. Malgus and Zaro oversaw the battle from their personal shuttle. Luke decided the battle couldn't cost anymore innocent lives, so he signaled the forces and miners to evacuate while he distracted them. Once Luke revealed himself on the battlefield, Malgus (who hadn't had a challenge with a Jedi in 3,000 years) chose to face him himself.
Back at the Jedi Temple, Destin and Rey both worked together to intensely student the datecube in order to unlock its secret. Chris, however, chose to meditate in order to calm is mind from the loss of his mother. As Destin kept examining the cube, he suddenly heard voice through the force, it said 'come to me, the galaxy needs me once more'. Though no one else could hear it, Destin knew someone said it, but couldn't tell who.
Back on Crait, Luke confronted Malgus alone as the troops evacuated.
Malgus: I see the Jedi haven't lost their persistence in interfering. I suppose it's their instincts that leads them to face us.
Luke: The Jedi act on the will of the force, and the balance within it that must be maintained. Where ever darkness rising, light will always be there to meet it.
Malgus: I've long awaited the day to be revived from my hibernation, at last I can face a Jedi and the galaxy once more.
Luke: You're wrong. Strike me down in hate, and I'll only grow stronger through the force as a spirit, to aid another Jedi to face you.
Malgus: I never planned to kill you, I wish to see your order and the Republic fall before your end. Now, I only wish to win this duel and have you for a trophy.
Luke and Malgus went toe-to-toe as the last few troops and miners fled from the base onto ships to escape into space. Malgus was too focused on Luke to sense the escape of his troops, and Luke refused to be overpowered by an 'ancient relic' like him. But Malgus sensed Luke's mind and feelings and preyed on them.
Malgus: Your Republic will lose this war to me, just as you lost your darling wife.
With Luke's heartbreak, he grew too weak to continue fighting and collapsed in guilt, believing his wife's death to be his fault.
Meanwhile, at the Jedi Temple on Coruscant, Chris' meditation was broken by what he'd sense; his father's defeat on Crait. When he went to tell the others, Destin had finally broken the codes on the datacube. It revealed the holo-image of an old Republic Jedi cruiser and a set of coordinates that led through space. Realizing they had to get involved, Chris, Destin, and Rey snuck on a ship and piloted it to the coordinates, not knowing what truly laid out there waiting for them.
Luke was taken prisoner on to Malgus' shuttle while he led his troops into the base, who'd already escaped into space. Realizing Luke distracted and slowed him down, Malgus roared in a fit of rage.
Chris, Rey, and Destin followed the coordinates to the outer rim world of Taris, a half-city-half-ruined planet. From their ship they noticed a ship on the surface that resembled the one in the holo, only covered in vines and decaying. Using their lightsabers, they cut down the vines and cut the door open. They explored the old, dark ship until coming to the cabins. Where they found 5 figures (3 humans (2 males and 1 female), 1 Chagrian, and 1 pure blood Sith) all frozen in carbonite. Along with 2 powered down droids (a C2 model protocol droid and a T7 astromech unit). Destin recharged the 2 droids while Rey and Chris worked to thaw out the figures from carbonite.
Destin then realized the blonde male human was a Jedi, in fact, it was Gorge-Wash Ington, his ancestor. The others with him were his apprentice and wife, Kira Carsen, and his companions, Sergeant Rusk, Doctor Kimble, and Darth Scourge (a pure blood Sith turned Jedi), and the droids were C2-N2 and T7-O1. After some recovery from the carbonite sickness, the kids informed the legends about how long they've been frozen, how they found them, and the state the galaxy is currently in. Then, T7 plugged into the ship's system and all the systems came to life and the ship began to fly. It was old, but not yet obsolete. Chris, Rey, and Destin gaze out with pride of what they achieved and confidence in what lied ahead of them.
All rights reserved to The Walt Disney Company and Lucasfilm Ltd. No copyright intended.