Beryl was born in Mirwell Province. She has long wanted to restore Mirwell to its former glory, albeit in an honorable, non-militaristic way. She fought hard as an officer in the provincial army to secure a place as Mirwell's closest aide. She has considerable experience as his chief interrogator. It is from this position that King Zachary has her planted as a spy to keep watch on the Mirwells, instead of running messege errands, as her ability it to deceive and convince someone of a role she portrays. Beryl is the one who slipped F'ryan Coplebay the message about Mirwell's plan to amuch the King's annual spring hunt and Amilton's coup.
She is discovered by Shawdell in Green Rider, but because Mirwell and Amilton and Shawdell are thwarted quickly and decisively, Beryl decides to return to Mirwell and watch Timas on the off-chance that she hasn't been discovered as the traitor there.
In The High King's Tomb, Beryl is unfortunately discovered when the wild magic went rampant. Her ability fails in the presence of a Second Empire operative named Birch, who suspects her affiliation with the Green Rider. Birch supplants her as Timas' aide and keeps Beryl out of the way by sending her out on one military manuever after another. She is caught overhearing Birch talk to a messenger for the Empire, and thus capture her. She is experimented on by Grandmother's magic spell that made it seem like she was being stabbed by golden chains, when in reality it was colored yarn. Karigan subsequently discovers and releases her upon Second Empire moving into the Teligmar Hills. Interrogating Immerez, who helped Second Empire into Mirwell, must be a long-held desire of Beryl's: she watched her older brother kill himself when she was younger. Immerez had scuffed Mirwell's saddle and blamed a young Rilery Spencer, so Mirwell had Riley's hands cut off; a man with no hands can't have a livelihood, so he threw himself off a cliff.
Upon returning to Sacor City, and being honored for years of service, it is decided by Mapstone and King Zachary that it is unsafe for Beryl to return to Mirwell. So she dons Rider green and resumes her long put-off swordmaster initiate training with Master Drent. Beryl rides a dark bay mare named Luna Moth. She is described as being tall and attractive, and is named for the green color of her eyes. Her eyesight isn't the greatest, so she carries with her a pair of spectactles.