While he used the same blue lightsaber that he always had in battle, that weapon wouldn't work after Kyle made his dark transition. Kylo disassembled the weapon later and retrieved the kyber crystal inside.
Kylo Ren might have accidentally cracked the crystal in Luke's lightsaber during that brief confrontation, claimed it for his own, and left Luke for dead in the rubble. By the time Luke emerged, Ben had already killed all of the Jedi in training or recruited them as Knights of Ren and burned the temple.
In the (canon) comic Rise of Kylo Ren #4 we see Ben "bleeding" the crystal from his original lightsaber, presumably at the urging of his master, Snoke. When he does so, it causes the crystal to crack.
Kylo Ren's lightsaber crackles because it has a cracked and unstable Kyber crystal that turned out the way it did after he poured his negative energy into it during the bleeding process of the crystal. Due to Kylo Ren's bottled-up emotions and confused state, the bleeding process made the crystal unstable.
We learned in The Force Awakens: The Visual Dictionary that the now-infamous red lightsaber had a cracked kyber crystal. Thanks to The Rise of Kylo Ren #4, we now know that the broken crystal is a result of the bleeding process.
A crystal embodies the Jedi as the heart of the lightsaber, and pure kyber has no color until it's bonded to the Force user. This process likely resulted in Rey Skywalker's lightsaber being yellow.
Even though Kylo Ren uses a red lightsaber, harnesses the dark side of the Force, and wears a cape, he is not a Sith. Because of that, he can never hold the title of Darth. Instead, he was just a chaotic mess of the dark side (until he eventually found his way back to the light).
The crossguard blades allow Ren's saber to operate safely – his weapon is constructed around a dangerously flawed kyber crystal, which would be overloaded if not for the lateral plasma vents that create the quillons.
The weakest and most harmless type of lightsaber is the one that has been “baby-proofed”: the training lightsabers. As the name implies, this type of lightsaber is only utilized in the context of training very young Jedi to one day become Jedi Masters.
Kylo Ren's lightsaber had a cracked kyber crystal, which generated an unstable blade. The excess power was vented out the sides, thus creating a crossguard-like design. The most important and prestigious vessels of the First Order had weapons upgraded with kyber crystals from some secret source in the Unknown Regions.
Masters. For other uses, see Finn (disambiguation). Finn, formerly designated FN-2187 ("Eight-Seven"), was a Force-sensitive human male stormtrooper who served the First Order until his desertion and subsequent defection to the Resistance during the First Order-Resistance War.
Rey's lightsaber was a yellow-bladed lightsaber that was constructed by the Jedi Rey Skywalker following the First Order-Resistance War.
Kylo Ren's reforged helmet was strengthened through Sith alchemy. Sarrassian iron was painstakingly applied between the shards of the shattered helmet, creating a bright red alchemical web that resembled crimson lightning or scars.
Construction. In the construction of a Sith lightsaber, individuals partook in a process known as bleeding. By ways of the Force, they would pour negative emotions, such as rage, hate, fear, and pain into kyber crystals. The process would result in the crystals gaining a distinctive crimson or red hue.
Given that she studied Luke's ancient Jedi texts and was trained by Leia, Rey most likely used a variation of Form VI, Niman. Form VI, Niman, takes elements from the previous five forms and combines them into a pastiche that's proficient in all situations, but lacks the specialization of other forms.
In 58 BBY, a young Mace Windu was sent to Hurikane on a mission as a Padawan. In exchange for helping the stone-encrusted native species, Windu was given a handful of the rare amethyst Hurrikane crystals, which he used to create his unique electrum lightsaber.
Form VII, known by its two primary disciplines of Juyo and Vaapad; and also known as The Ferocity Form, was the seventh form of lightsaber combat. It was considered the most aggressive and unpredictable form.
The General and Obi-Wan dueled, and despite wielding four lightsabers at once, Grievous was dismembered and once again tried to flee. Obi-Wan gave chase, and the two eventually fought in a knock-down drag-out fist fight.
The Firebrand was a basic design of lightsaber hilt that was used by Jedi Initiates as well as Knights of the New Jedi Order as of 14 ABY. An all black hilt, it was known to have a stable grip and was equipped with a thin deflector ring to protect the wielder from energy backlash.
While he is not Force-sensitive, Grievous has been trained in all forms of lightsaber combat by Count Dooku. Each of his mechanical arms can separate in half, allowing him to wield four lightsabers at once to overwhelm his enemies.
Lightsaber Colors Used to Matter
A brief who's who of users with blue lightsabers includes Obi-Wan Kenobi, Luke Skywalker, Anakin Skywalker (Hayden Christensen, pre-youngling slayer), Shaak Ti, and Count Dooku (Christopher Lee, pre-dark side/ass handed to him by Yoda).
In The Last Jedi, during Rey and Kylo Ren's confrontation in Snoke's throne room, Luke's original lightsaber was split in half, and as shown later on in the movie, the crystal had been divided too, but in The Rise of Skywalker, which takes place one year after the previous movie, Rey is shown to have rebuilt it.
1 Darth Sidious
As well as being a gifted bladesman Sidious' connection to the Dark Side is extremely powerful, granting Sidious the ability to conduct force lightning.