My theory is that Darth Maul is being set up as a bridge between Star Wars: Maul – Shadow Lord, Solo: A Star Wars Story, and Star Wars Rebels.
The entire season builds toward Devon embracing rage. Maul constantly tells her that rage is a tool, but she resists until Darth Vader kills Daki. That completely breaks her. She uses half of Maul’s saber, nearly kills the 11th Brother, and then charges Vader without fear.
Then we get the finale scene where Maul stops her, tells her she isn’t ready, and promises to train her. On the ship, she’s crying, has Sith eyes, and accepts him as her master. That feels like the beginning of her true dark side arc.
At the same time, the finale directly sets up Maul’s rise in Crimson Dawn because Dryden Vos offers him a deal that leads perfectly into Solo: A Star Wars Story.
I think Maul trains Devon into a canon version of Darth Talon. She’s a Twi’lek, has similar visual traits, and Dave Filoni has a history of reworking Legends characters into canon.
Devon is also clearly far too skilled to be killed off by an Inquisitor. Even before fully embracing her rage, she was able to hold off both Marrok and the 11th Brother at different points despite struggling. Once she fully taps into her rage, she nearly kills the 11th Brother and even manages to briefly hold her own against Vader despite him being far stronger, more experienced, and more powerful in the Force. The show clearly framed her as someone with huge potential.
A lot of people think Devon will eventually betray Maul, but I don’t buy that. Maul doesn’t handle betrayal well at all. The syndicates abandoned him after Star Wars: The Clone Wars and he never let that go. He was devastated when he lost Savage Opress, and throughout Shadow Lord he repeatedly risks his life and exposure to protect Devon. If Devon simply abandoned him, I think Maul would obsess over revenge against her the same way he does with everyone else who betrays him.
That’s why I think Darth Vader kills her instead.
Devon already wants revenge on Vader, Marrok, and the 11th Brother, and I think Crimson Dawn eventually grows enough that the Empire sends Vader to deal with it. Devon dies trying to kill him.
That death would make perfect sense for Maul’s arc because the Sith took everything from him: his childhood, his family, his brother, and now his apprentice. It would deepen his hatred for both Darth Sidious and Vader.
After losing Devon, Maul continues building Crimson Dawn but eventually goes to Malachor for ancient knowledge to defeat the Sith, leaving Qi'ra in control, which connects to Solo.
Then Ezra Bridger changes everything. Maul sees him as a potential apprentice against Vader and Sidious, but when he discovers Obi-Wan Kenobi is alive, his obsession with revenge takes over again—which leads directly into his ending in Rebels.
I think Devon has to die because if she survives, there are too many unanswered questions about where she is during Rebels and later canon. Her death would also strengthen Maul’s tragic arc, which I think is the entire point of the show.