Phobos and Deimos

Most of the time the pair look like two plain black crows. When they take human shape they become near-identical twins, told apart only by the color of their leotards, red for Phobos and purple for Deimos, each marked with a black emblem echoed on their silver earrings. Long black hair falls to their backs, gathered into big buns beside their ears with loose strands trailing down the front, and broad white bows sit behind them above their high heels. Both have pale skin and blue eyes. They arrive tiny and almost fairylike when they first turn humanoid in the Dream arc, then appear at full height in the Stars arc, standing a touch shorter than Sailor Lead Crow.

To Rei the twins are equal parts pets, protectors, and advisers. She plays fetch with them using her ceremonial arrows, and they aid her fire readings and offer guidance, though unlike the talking cats they can speak only while in humanoid form. Once warriors in training on Coronis, they were singled out by Princess Mars to serve at her side, and their devotion to her and to their homeworld runs deep enough that they flatly refuse to accept Sailor Lead Crow's turn to Shadow Galactica as anything but treason.

Rei knows the crows from early childhood, calling them by name at Hikawa Shrine before she even starts school, and after her mother dies and she moves to the shrine she raises them almost as pets. In the manga's Dark Kingdom arc they dive at Usagi on her first visit, which makes Rei sense an evil aura and blast her with Akuryo Taisan by mistake. Rei later calls on Phobos and Deimos as an attack against Jadeite, and the birds resurface through the Casablanca Memory story and see the Guardians off before their journey to the Moon.

The Dream arc brings their humanoid debut: after the Dead Moon Circus arrives, they rescue Rei from Tiger's Eye inside the Mirror House, reveal their true forms, and hand her the Mars Crystal so she can become Super Sailor Mars. Their story turns tragic in the Stars arc, when Sailor Lead Crow tracks them to the shrine. She was once their fellow trainee on Coronis, left behind and bitter when Princess Mars chose the twins and gave them the planet's moons. The pair reject her claim to guardianship, and Lead Crow kills them and steals their star seeds, learning too late that Coronis itself has fallen to Shadow Galactica. Crystal follows the same beats, from the Hikawa Shrine attack through the Eternal mirror-house rescue to their deaths in Cosmos.

Outside the manga they stay simple crows. In the 90s anime they warn Rei of Jadeite's energy-draining plot and later harry Zoisite during the Rainbow Crystal storyline. The live-action series shows them only as unnamed digital ravens whose cawing startles Usagi, and in the musicals they appear variously as villain impostors, agitated birds, or operator-run puppets that help save Rei and deliver her transformation pen. They also lend their name to one of Sailor Mars' arcade-game attacks.