Hilda de Polaris is the high priestess of Asgard and the representative of the god Odin on Earth, ruling over the icy realm located in the far northern reaches of Europe. She is a young woman of nineteen years with long silver hair and blue eyes, who resides in the Valhalla Palace. Her sacred duty is to pray daily before the frozen sea of the Arctic Ocean, using her spiritual power to maintain the great glaciers and prevent them from melting, which would flood the rest of the world. As a ruler, she is generally portrayed as a kind, pacifistic, and deeply caring individual who is faithful to Odin and loved by her people; she worries about the well-being of her subjects and endures the harsh conditions of Asgard with a sense of resignation for the greater good of the planet.

This peaceful existence is shattered when she is corrupted by the malevolent Nibelung Ring. While praying, the sea god Poseidon (secretly manipulated by Kanon) attempts to persuade her to declare war on the Sanctuary of Athena, but Hilda refuses, stating her aversion to violence. In response, Poseidon forces the ring onto her finger against her will. The ring fundamentally alters her personality, transforming her from a benevolent priestess into a cold, ruthless, and ambitious leader. Under its influence, she declares war on Athena, seeking to conquer the world and expand Asgard's dominion so her people may live in a land where flowers can grow, though this ambition is described as a sickness born from the ring's dark magic.

Hilda's primary role in the Asgard saga is that of the main antagonist. She awakens the seven legendary God Warriors, each representing a star of the Big Dipper, to be her generals in the coming war. She commands the God Robes to awaken and leads her forces against the Bronze Saints who arrive to rescue Athena. Her motivations are complex; while she appears to be a tyrannical dictator seeking world domination, she is ultimately a tragic figure. It is later revealed that her true spirit was locked away inside the ring, forcing her to watch helplessly as her beloved warriors were defeated and died one by one, psychologically torturing her.

Several key relationships define her character. The most important is with her younger sister, Freya (also known as Flare). Freya is the first to recognize the evil change in Hilda and bravely defies her, escaping the palace to seek help from Athena. The bond between the sisters forms the emotional core of the saga. Another significant relationship is with Siegfried of Dubhe Alpha, the leader of the God Warriors. He is described as her greatest admirer and remains loyal to her, but ultimately discovers she is being manipulated; in his final moments, he tears the Odin Sapphire from his own God Robe to give to the Saints before sacrificing himself to help free her.

The character undergoes a clear arc from villain to redeemed ruler. Despite possessing no innate combat abilities, while under the ring's control Hilda wields powerful magical force that she can project as energy attacks. She is able to directly confront the Saints and Athena using this power. The only way to break the spell is to gather the seven Odin Sapphires embedded in the God Warriors' armor to awaken the legendary sword Balmung. After Seiya of Pegasus dons the Odin God Robe and uses the Balmung to destroy the ring, Hilda collapses, bleeding and freed from the curse. She immediately returns to her gentle personality, is wracked with guilt for the deaths of the God Warriors, and prays to Odin for forgiveness. She then risks her own life to help Athena and the Bronze Saints journey to Poseidon's underwater kingdom to continue their fight. Her suffering does not end there; wracked with guilt and having expended massive amounts of Cosmo to save both Asgard and Athena, she later falls mysteriously ill, a testament to the heavy price she paid for her corruption and redemption. Her story continues in the series Saint Seiya: Soul of Gold, where she continues to serve Odin and aids the Gold Saints against the god Loki.