Warning! SPOILERS for Obi-Wan Kenobi.
There may be a personal reason why Third Sister/Reva (Moses Ingram) is bent on hunting down Obi-Wan Kenobi (Ewan McGregor) in the ongoing Darth Vader (Hayden Christensen) is also confirmed for Obi-Wan Kenobi, its primary villain is a new character named Reva.
Set 10 years after Star Wars: Revenge of the Sith, Obi-Wan Kenobi sees the titular Jedi Master still hiding in Tatooine following Order 66. The first two episodes of the show have already been released, revealing the state of the galaxy. At this point, the Galactic Empire is still scouring for Jedi who survived Emperor Palpatine's (Ian McDiarmid) massacre, sending Inquisitors to do the job. While the Grand Inquisitor (Rupert Friend) and the Fifth Brother (Sung Kang) are more relaxed in carrying out their mission, Reva is obviously most keen on hunting down Obi-Wan.
Reva's eagerness to track Obi-Wan can be simply chalked up to the ambition. After all, nabbing the Jedi Master and delivering him to Darth Vader would immediately gain her prominence in the Empire. The Grand Inquisitor and the Fifth Brother both criticized her in the show, highlighting conflict among supposed allies. That being said, it's possible that there's an entirely different reason why the Third Sister is so motivated to catch Obi-Wan. There's a chance that Reva's motivation is personal more than professional. As Obi-Wan noted, some of the Inquisitors are previous Jedi. Perhaps Reva was once a Jedi Knight who once had a working relationship with the Jedi Master and feels betrayed by the Jedi High Council after it failed to protect them. This would also explain why the Third Sister is aware that Anakin is alive and is now known as Darth Vader — something that is a closely guarded secret.
Considering the fact that the Grand Inquisitor openly expresses his disdain for Reva, this particular theory makes sense. Perhaps the Grand Inquisitor doesn't see her as an equal given her origins. This further fuels the Third Sister's anger towards Obi-Wan in Obi-Wan Kenobi. Interestingly, this is a great way to set her up as a formidable main villain in the show which is a difficult feat given Darth Vader's confirmed appearance. Ultimately, however, Obi-Wan's final stand in the Disney+ show will be against his former Padawan. Reva could successfully track down the Jedi Master and rattle him out of hiding, which would establish his whereabouts leading to his arrest. Otherwise, the Third Sister attempts to take Obi-Wan out herself but fails. Either way, it's safe to assume that Reva's personal story will have ties to Obi-Wan, explaining her eagerness to see him captured.
At this point, Obi-Wan hasn’t figured out Reva's possible true identity. That's understandable given their limited interactions thus far. That being said, assuming that the Third Sister was once a Jedi Youngling, it's only a matter of time before Obi-Wan Kenobi figures out who she really is, effectively explaining why she intensely hates him.
Obi-Wan Kenobi airs Fridays on Disney+
