Briar is a character first introduced in The Teal Mask DLC expansion for Pokémon Scarlet and Violet. She is a teacher who works at the Unova region's Blueberry Academy.
The player,
Florian or
Juliana, first meets Briar when they get picked to go on a school field trip to the region of Kitakami, serving as the guardian for said trip. Briar's ancestor is Heath, the man who originally went on an expedition to Area Zero and wrote about the amazing sights he saw there, including the Pokémon Terapagos. Due to Heath's work being discredited, some of it blanked out, for it sounding too much like a fairy tale, it had inspired
Briar, who owns the original manuscript of Heath's work, to find Terapagos for herself and learn more about the Terastal phenomenon to prove he was correct after all these years.
This dream finally takes hold in the post-game of the Indigo Disk DLC arc in the game, where Paldean champion
Geeta and Elite Four Member
Rika give her permission to go into the Indigo Disk. Briar takes along the player,
Kieran, and
Carmine, and go deeper into the depths of Area Zero than previously explored. There, she is unaware of the conflict between the kids, and leads them deeper and deeper, prioritizing her own excitement and discoveries. She accidently causes trouble when she has Kieran, who caught Terapagos, try Terastalizing it, making Terapagos unstable. She takes regret in causing trouble to the students, and writes a book about her experiences without mentioning you or the other character's names.