Back when this show was first announced I jokingly referred to Devon (before we knew her name and just knew that Maul was training a Twi'lek girl a year after Ahsoka blew him off) as "Maul is creating Ahsoka's Wario" but the thing is. That really is kinda it, conceptually.
By which I mean: the thing Ahsoka and Devon have in common in a Doylist sense is that they are both original characters created to be a legacy character's apprentice (Anakin for Ahsoka, Maul for Devon) in a show that legacy character was nominally the lead of which existed between already-set points in their established timeline.
Which means: those apprentice characters are ultimately where the real action is. Because while the elaboration on how the legacy characters get from A to B is far from unwelcome, we know how things end for them, we know where their characters ultimately end up: Anakin becomes Vader and Maul dies to Obi-Wan on Tatooine. We learn the how, the why, but we already knew the what.
But Devon in Shadow Lord is wide-open, as Ahsoka in Clone Wars was before her: she's new, she has no fixed end, anything is possible! What happens to her? Where does she end up? Who does she become? These are the questions! And so once again the apprentice girl OC is ultimately the one to watch. Ahsoka outgrew her association with Anakin as people began to care about her in her own right and I have no doubt the same will be true for Devon and her association with Maul.
The "Wario" part is still tongue in cheek but, well, not inaccurate: Devon is the dark mirror of Ahsoka's character on that conceptual level, because this is a show about, in Sam Witwer's words, bad guys versus worse guys. And where Ahsoka ultimately learned to be better at being Anakin than Anakin was and thus never fell to the dark side, I think Devon will give us the answer to what happens when someone learns how to be better at being Maul than Maul is.