Alcyone is the first antagonist the Magic Knights encounter, as she has been ordered by Zagato to destroy the three girls from another world so that the legend of the Magic Knights never comes true. She is a powerful adversary whose attacks and spells are ice-based. She has the ability to summon beasts from the spirit realm. Alcyone is the most loyal and arguably strongest of Zagato's followers, because she is motivated by love. However Zagato does not return her feelings and uses her loyalty rather heartlessly. In the second season of the anime, Alcyone returns under mysterious circumstances.
In the manga she is killed by Zagato after failing him twice.
In the anime she lives on until near the end of the second season; moments after Zagato and Emeraude's deaths, she's captured by the evil witch Debonair, who brainwashes her into becoming her slave. Lantis captures her and holds her prisoner inside The Castle of Cephiro, she shatters the sphere she was captured in though it rendered her unconsious. She is then used by Debonair as a gateway to allow her monsters to enter the castle thereby terrorizing the people and increasing Debonair's power.Alcyone is then stripped of her memories. When she recovers them, she reveals Debonair's plans for Cephiro and Debonair's location, and is killed shortly after by Debonair for her betrayal.
Her name is occasionally misromanized as "Alcione"--this was featured in the first run of the English translation. Her name comes from the Subaru Alcyone SVX. She is voiced by Barbara Goodson and Yuri Amano.