Frey

Frey (also known as the Sky Queen) is a harpy and one of the former members of the Ten Great Demon Lords in the anime That Time I Got Reincarnated as a Slime.

She is the queen of the harpies and rules over winged creatures, having ascended to that position in the past. In the anime, she appears as a striking, buxom woman with white hair, yellow eyes, bird-like talons for feet, large wings on her back, and a red gemstone on her forehead. She typically wears a revealing, off-the-shoulder red outfit resembling a leotard with a deep neckline. (She can retract her wings and transform her talons into human-like legs to blend in if needed.)

Personality-wise, Frey is careful, cunning, and strategic rather than arrogant—she's humble enough to admit her own limitations as a Demon Lord. She's shown to be clever in schemes (like teaming up with Milim to outmaneuver others such as Clayman), and she develops a close, almost maternal/protective relationship with Milim Nava, eventually stepping down from her Demon Lord status to become Milim's subordinate and trusted aide.

She first becomes prominent around the events involving Walpurgis and the shifts among the Demon Lords in Season 2.