The Obi-Wan Kenobi Disney+ TV show marks the live-action debut of Fifth Brother, one of Darth Vader's Inquisitors - and the character was based on an unused design for Kylo Ren in Star Wars: The Force Awakens. Introduced in Star Wars Rebels, the Inquisitors were established by Emperor Palpatine to support Darth Vader in his most important task; to hunt down Jedi survivors of Order 66, and thus ensure the light of the Jedi was snuffed out for good. They consisted of Force-sensitives and former Jedi who had been twisted to Palpatine's will.
The Inquisitors certainly look imposing, clad in sweeping black cloaks and wearing masks designed to conceal their identities and thus dehumanize them. It's unclear whether these masks were forged for them, or whether they are ancient Sith relics tainted by the dark side; if the latter, those masks may well have been chosen to boost their aggression and anger, giving them a brutal edge in battle against the Jedi. The Inquisitors were given unique lightsabers that could actually double-up as a sort of Force-propelled helicopter, allowing them to pursue Jedi with tremendous speed. Several Inquisitors will be appearing in the Disney+ Obi-Wan Kenobi TV series - including Fifth Brother, played by Sung Kang.
Back in 2019, Lucasfilm's Creative Art Manager took to Twitter to reveal Fifth Brother was actually based on a very early concept for Kylo Ren, named the "Jedi Killer." It's an intriguing design, appearing to suggest the Jedi Killer may not have originally been humanoid at all, because there's something distinctly inhuman about it; the respirator - which was ditched - is even more evocative of Darth Vader than Kylo Ren's final outfit. It's easy why Lucasfilm decided not to abandon this concept outright, but rather tied it to Darth Vader as one of his Inquisitors.
This may not be the only Kylo Ren design to have influenced the Inquisitors. Although Lucasfilm has not confirmed any other direct connections, there are similarities between different masks sketched for Kylo Ren and the masks worn by other Inquisitors. Meanwhile, it's interesting to note there's a visual throughline between the Inquisitors and the Knights of Ren in the sequel era, perhaps originally intended to be a hint that Darth Vader's servants evolved into Kylo Ren's. If that was indeed deliberate, it's been ditched, because tie-ins have since hinted the Knights of Ren have a long and distinct history in the galaxy; their leader Ren operated in the Imperial era, and even crossed paths with Darth Vader on occasion.
Still, Fifth Brother's design certainly serves to underline the fact that nothing is ever wasted. Even early concept art - usually created before the story had been locked down, and thus exploring ideas never brought to life - can be repurposed. In this case, an unused design from Star Wars: The Force Awakens made its way into a Star Wars animated series through the Inquisitors' Fifth Brother, and is now being translated into live-action form in Obi-Wan Kenobi.