Member of the Black Moon
Berthier has blue eyes and white hair, which she wears in a single braid. She wears a light blue leotard, with matching heel boots and her hands are wrapped in bandages. Like all members of the Black Moon Clan, she has the Black Moon symbol on her forehead.
Berthier was a member of the Black Moon Clan serving under Rubeus, deployed after Koan's defeat by Sailor Moon. She claimed to be a water diviner, and used a shard of the Black Crystal. She recognized Ami as Sailor Mercury when she was able to locate a broken water pipe beneath the school grounds and challenged her to a chess match. Berthier used the Black Crystal shard to choose the right moves, all the while taunting Ami that she was alone. She also offered a wager: If Ami won, Sailor Mars would be returned to them, but if she lost they must hand over the Rabbit. With Usagi's encouragement Ami beat Berthier in the chess match. Berthier took the offensive and Sailor Mercury chased her into the lot, only to be confronted by Berthier and a bunch of Droids. Though Sailor Mercury created illusions of herself, Berthier used her water powers, causing underground water to spout and enclose Sailor Mercury in a sphere of water. Sailor Moon arrived and used Moon Princess Halation to destroy Berthier, but the sphere still held Sailor Mercury, who was then kidnapped by Rubeus.
Berthier has the power of water. Her water is strong enough to trap or encase a person within it.