She is a young woman with blue eyes, white hair in a braid, and the Black Moon symbol on her forehead. She wears a blue leotard, blue gloves, and blue boots.
After being purified by Sailor Moon due to being convinced by Koan, she wears casual outfits. She also wore two primary casual outfits; her first outfit is a red and black checkered sleeveless short dress and black high heels. She also accessorize it with a necklace with a red diamond pendant in the center. She wears this during the chess competition and her second outfit is like from her first outfit is a white long sleeved formal suit jacket with a red and black checkered sleeveless undershirt, black slacks and her black high heels from her first outfit. She no longer has an extra braid on her forehead.
Sailor Moon R
After Koan left the Ayakashi family, Rubeus sent Berthier to take over a crystal point in a chess building. Ami Mizuno encountered Berthier and transformed into Sailor Mercury to fight her, revealing her true identity to her. Berthier retreated from the battle and entered the chess tournament where she faced Ami in the finals. Although Ami won, Berthier trapped the other Sailor Senshi in a ball of ice and started another game of chess with Ami, except this one was with her own rules - whenever Ami lost a piece, a part of her body would freeze. The spell was shattered by Tuxedo Mask, who freed all the Sailor Senshi and Berthier's plan was foiled. Calaveras and Petz had appeared to reclaim some of the credit when Berthier's had the advantage but explained that Rubeus was going to kick her out for her failure and abandoned her. Berthier, alone and out numbered, broke down and attempted to freeze herself and the entire Senshi to death. Kōan convinced her to stop and change her evil ways so Sailor Moon used Moon Crystal Power on her.
Berthier was later captured along with Koan by Calaveras and Petz, in an attempt to turn them evil again but in the battle that followed, Rubeus ditched Calaveras and Petz and they were also healed of their evil. Berthier is the second of the Ayakashi Sisters to turn good and she happily mocks Petz for being old and grouchy when she and her sisters open a cosmetic shop together.
- Berthier is the Ayakashi Sister counterpartner of Sailor Mercury, as they both use water-based attacks.
- Bertheir is forcibly changed back to her evil self by Apsu and is a boss fight in Sailor Moon RPG Another Story. However, she like her sisters, seem to still have control of their own minds, as they tell the senshi they don't want to fight them, but their bodies are forced to fight the senshi, in this battle, the senshi are forced to kill them. It is unknown if they were revived at the end.
- Berthier is named after berthierite, an iron sulfide.
- Her DIC English voice actress, Kathleen Laskey, is also the current voice actress of Geraldine Husk the villain of the American cartoon series, Totally Spies!
- Interestingly, her voice portraying Geraldine is much like Berthier.