Cal is going to become stronger in the force in Jedi: Fallen Order as players progress through the story. He’s also going to attain new skills along the way, and relearn much of his training when he was in the Jedi Order. Eventually, players get the chance to repair Cal’s broken lightsaber to have it become a double-bladed weapon.
To get the technology for Cal to repair his partially broken saber, you need to travel to Dathomir. You don’t need to go too far on the planet, though. You’ll know you’re on the right path when you encounter a Nightsister and the Nightbrothers, the male Zabraks. Fight a few of them, and progress through the story. You’re going to end up at the location pictured below.
It’s a little off the beaten path, but you can find it shortly after you open up Dathomir’s first shortcut in Brothers’ Bastion. Go to the workbench, and you’re going to enter a brief cutscene. Cal is going to add some new repairs to his lightsaber, and shortly after he finishes, he’s going to display his completed double-bladed saber.
There are multiple locations available for players to acquire the double-bladed lightsaber. However, this is the quickest and most natural method.
Moving forward, players can now choose what style of lightsaber they want to use during combat. They can change the style by hitting the right button on the directional pad while in combat. Hitting it switches between Cal’s single-blade and double-bladed combat styles. Out of combat, you want to hit the left button on the directional pad to switch between the styles.