Hyperia, known as Themis in the original Japanese version of the 1981 film, is the Goddess of Fire and the sovereign ruler of the land. She is a central figure in the backstory of the anime, as her personal history directly creates the conflict that drives the narrative. Characterized by her regal presence, Hyperia is depicted as a woman with striking red hair who resides in a grand Fire Palace. She is the mother of Princess Malta, the film's female protagonist, and the older sister of Oceanus, the God of Water who rules the sea.

In the ages before the story begins, Hyperia and her brother Oceanus existed in harmony, their domains coexisting as one. This peace was shattered by the jealous schemes of Algaroc, the Lord of the Winds, who deceived each sibling into believing the other was plotting a betrayal. The resulting war between the Fire Clan and the Water Clan nearly destroyed both sides. Even after the highest god intervened to punish Algaroc, the rift between Hyperia and Oceanus remained, forcing the elements apart. To protect her children and maintain the new, fragile order, Hyperia created the Holy Flame near the edge of the sea, a sacred fire she believed would keep the waters calm and ensure her people would never be extinguished. It was this tragic misunderstanding that led to an unyielding law forbidding any interaction between the Fire Children and the Water Children.

As a result of this past trauma, Hyperia is deeply protective of her domain and her daughter. She is a strict and formidable leader, motivated by a desire to preserve her kingdom and enforce the separation from the water realm. Her primary role in the story is as an authority figure and an obstacle, representing the longstanding prejudice and the institutional barrier that the young lovers, Malta and Sirius, must struggle against. Her decree is the fundamental law that makes their romance forbidden. When her daughter begins to show sorrow and disobedience, Hyperia firmly reminds Malta of her duties, including the impending ceremony where she will officially become Queen of the Fire Clan, ending her guardianship of the Holy Flame.

Hyperia's most significant relationship is her complex bond with her brother, Oceanus. Once close, they become bitter rivals and cautious co-rulers of separate worlds, each enforcing their own isolationist policies. Her relationship with her daughter, Malta, is also central; while she clearly loves her child, her authority and fear of the water clan make her seem harsh and unyielding. Her judgment is also clouded by a personal history with Sirius’s father, as she and Oceanus were once good friends with him before believing Algaroc's lies, a fact that adds a deeper layer of animosity to the feud.

Despite her rigid stance, Hyperia is not a villain but a wounded figure. The story presents her development primarily through reconciliation. Witnessing the ultimate sacrifice of her daughter Malta and the water prince Sirius—who give their lives for each other—shatters the centuries of mistrust and anger. Their pure, selfless act of love demonstrates the falsehood of Algaroc's original lies and proves that fire and water can indeed coexist. In the end, this tragedy leads Hyperia to forgive Oceanus, finally ending the war and allowing the two clans to begin healing. As a deity, her notable abilities include the creation of the powerful Holy Flame, command over the element of fire, and rulership over all the land and its inhabitants. Her actions, born from a place of betrayal and a fierce desire to protect her own, set the stage for the entire tragic romance.