Arihnda Pryce is a human Imperial governor, and the rarest kind of Star Wars villain: one whose entire motive is a property dispute. She is from Lothal, she is named in Jason Fry's young-reader novel Servants of the Empire: Edge of the Galaxy (2015), she first appears on screen in the Star Wars Rebels season-three premiere "Steps Into Shadow" (2016), voiced by Mary Elizabeth McGlynn, and her full history is told in Timothy Zahn's Thrawn (Del Rey, 2017).
The mine
Zahn's novel runs her chapters in parallel with Thrawn's, and the contrast is the point. Her family owns a doonium mine on Lothal. Governor Azadi forces them to sell it to the Empire. Pryce goes to Coruscant to fight the decision, discovers that nobody there can be appealed to and everybody there can be traded with, and never goes home in the sense that matters.
How she climbs
She does it with information. She gathers leverage on Moff Ghadi, on Senator Renking, on the Higher Skies group, and she spends it precisely. There is no combat and no Force in her half of Thrawn; there is a woman learning that the Empire is a machine for converting other people's secrets into your own advancement. Grand Moff Tarkin makes her governor of Lothal, which is exactly the prize she wanted: she comes back owning the planet that sold her out.
Governor
As governor she turns Lothal into an industrial centre and cannot stop the rebellion growing inside it. Her weakness is temperament. She destroys a fuel depot to kill a handful of rebel leaders, taking Thrawn's TIE Defender production capacity with it and earning his open contempt — the single clearest illustration in the franchise of the difference between an ambitious administrator and a strategist.
The end
Captured by rebels during the liberation of Lothal and coerced into surrendering access codes, she is offered a way out and refuses to take it. She dies when the Imperial Complex self-destructs. It is a genuinely difficult ending to read, because the show declines to make it either noble or pathetic.
What she is for
Pryce is the answer to a question the Empire's screen villains usually dodge: who actually staffs this thing? Not Sith, not admirals, not zealots. People from somewhere, with a grievance and a mortgage, who found that collaboration paid. Zahn writes her as the most ordinary person in the book and by some distance the most frightening.
Where to read her
Thrawn, which is as much her novel as his, then Rebels seasons three and four.