Alcyone is an ice sorceress who tutored under Clef and was brought up to attend to the Pillar. However, she fell in love with the high priest, Zagato, and for this love became his servant, although the affection is entirely one-sided.

Spoiler

In the manga, she is killed after failing Zagato not once but twice. In the anime, she lives on until near the end of the second series; few after Zagato and Esmeraude's deaths, she's captured by the evil witch Debonair, who brainwashes her into becoming her slave. Lantis captures Alcyone in battle, but she has lost her memories; when she recovers them, she reveals Debonair's plans for Cephiro and Debonair's location, but her former mistress kills her before she can finish. In the Sega Saturn game, Alcyone appears to die, then comes back near the end of the game in the later part of Zagato's palace.

Her name is occasionally misromanized as "Alcione"--this was featured in the first run of the English-language manga. Her name comes from the Subaru Alcyone SVX. (Source: Wikipedia)