While Arya is a significant character throughout the series, she is not physically present in the third book, "Inheritance."
Here's why:
* She is trapped in the realm of the Dragon Riders: In "Eldest," Arya is taken captive by the Ra'zac and imprisoned in a hidden chamber in the Varden's stronghold. This realm is separate from the mortal world, and she remains there throughout "Brisinger" and "Inheritance."
* Her influence remains: Even though she's absent physically, Arya's presence is felt through her influence on Roran and Eragon. Her wisdom and strength guide them in their decisions and actions.
* Her story continues: While she doesn't physically appear in "Inheritance," her fate is ultimately revealed, and her journey in the realm of the Dragon Riders culminates in a significant moment.
So, while Arya isn't physically present in the third book, her absence is significant and her story is intertwined with the events of "Inheritance."