Moviegoers will never forget the moment we first saw Darth Vader's menacing visage. The Dark Lord of the Sith cut a threatening figure, and his mask removed all trace of humanity. He was raw, imposing, and terrifying in his viciousness.
When Lucasfilm introduced us to Kylo Ren, we expected something similar. After all, his sweeping black robes and armor were clearly evocative of Darth Vader himself. He even wore a helmet, one that seemed carefully designed to be every bit as inhuman as Vader's own. Then, to our surprise, the character spent most of The Force Awakens with the helmet removed, stressing his very humanity.
So why does Kylo Ren wear a mask in the first place, if he's only going to remove it all the time? Lucasfilm has just provided an official answer, with a quick explanation offered at the Star Wars booth at #NYCC2017:
"Kylo Ren is the son of Han Solo and Leia Organa, protégé of Luke Skywalker, and eventual Master of the Knights Of Ren. He is known as the ‘Jedi Killer’ among the rank and file of the First Order. His helmet was crafted to mask his visage and voice, concealing his identity as he delves further into the power of the Dark Side of the Force."
Ben Solo No Longer
Sith Lords take on a new name in order to make a powerful statement. Some choose a new name for themselves, but for others it is given by their Master. Always it is a declaration that they have embraced a new identity. That's why Palpatine takes such pleasure as he renames Anakin Skywalker "Darth Vader." The Chosen One, trained by the Jedi, might as well be dead. A new, terrifying being has risen to power in Anakin Skywalker's place.
It seems that Kylo Ren's path has been very different, and a lot less dramatic. Rather than forge a new identity as a celebration of the dark side, Kylo Ren has instead used it to conceal who he is. He wears a mask so that his visage and voice can be hidden, so that the world around him will not know he is actually Ben Solo, son of Han and Leia. His mask is no symbol of his new identity. Rather, it is an attempt to hide from his old one.
This subtle explanation reinforces some key themes in The Force Awakens. #KyloRen was caught between the light and dark sides of the Force. He may have committed to the First Order, he may have led the Knights of Ren in battle against the Jedi, but Ben Solo still wasn't wholeheartedly dedicated to the dark side. That's why the death of Han is so moving, as Han offers his lost son one last chance to return to the light.
The themes fit perfectly with Kylo Ren's mask, deliberately designed to remind him of the dark side, but taken off so many times as he was still seduced by the light.
If that's the case, we should expect the Kylo Ren of #TheLastJedi to be very different. He has killed his own father, and in so doing committed himself to the dark side. We'd expect Kylo Ren to keep his helmet on in this film.
The Acolytes of the Beyond
There's likely another reason Kylo Ren wears a helmet, though, teased by Chuck Wendig's novel Aftermath: Empire's End. That canon story introduced us to a brutal dark side cult known as the Acolytes of the Beyond, who seem to have been subtly influenced by Snoke himself. The Acolytes of the Beyond grew in influence in the years before Kylo Ren's fall, launching terrorist attacks across the Galaxy. Importantly, they venerated Sith artifacts — particularly helmets.
They believed these ancient Sith artifacts to be soaked in the dark side of the Force. In one telling scene, a member of the Acolytes donned a Sith helmet, and was transformed. She lost all trace of doubt and fear, and was reduced only to bloodlust and rage. Intriguingly, that mask was described in such a manner as to be very similar to the one Kylo Ren would ultimately wear. It may not be the same one, but they're clearly conceptually linked.
If that's the case, then the mask becomes even more intriguing. Not only was Kylo Ren's mask an attempt to conceal his own identity, it was also a way for the wearer to continually immerse himself in the dark side. The fact Kylo Ren kept removing his mask in The Force Awakens becomes tremendously significant, suggesting just how much Ben Solo was actually struggling against the darkness.
The reality is that Lucasfilm didn't go into the Prequel Trilogy with a concrete plan. As a result, these explanations are essentially retcons, exercises in retroactive continuity. For all that's the case, the great thing is that these retcons dovetail perfectly with Kylo Ren's themes and character arc in The Force Awakens. That makes them pretty impressive, and exciting to see.