Alcyone is an ice sorceress trained in magic by Clef, originally tasked with protecting Cephiro's Pillar, Princess Emeraude. She betrayed Clef and Emeraude, pledging service to High Priest Zagato out of romantic love for him, becoming one of his most devoted followers. Her abilities focus on ice-based magic and summoning, including Ice Attack (barraging icicles), Ice Spear (sharp spear-like icicles), Ice Blade (large blades erupting from the ground), Frozen Finale (a potent blizzard), and summoning creatures like a two-headed lupine beast. She also casts Astora (a lightning bolt).

Her story varies across adaptations. In the manga, after repeated failures to eliminate the Magic Knights on Zagato's orders, he executes her for incompetence following her second failure.

The anime extends her role. After Zagato and Emeraude die, the witch Debonair captures and brainwashes Alcyone into servitude. Later imprisoned by Lantis within the Castle of Cephiro, she escapes her prison sphere, collapsing unconscious from the effort. Debonair then uses her as a conduit to send monsters into the castle, amplifying her own power. Alcyone eventually regains her memories, exposing Debonair's plans and location, leading Debonair to kill her for this betrayal.

In the OVA, Eagle Vision kills her by choking her after she fails to defeat Hikaru.

Her name, occasionally mis-romanized as "Alcione" in early English translations, originates from the Subaru Alcyone SVX automobile.