In the original Voltron: Defender of the Universe continuity, Haggar is a powerful and sinister witch who serves as the primary advisor to King Zarkon, the ruthless ruler of Planet Doom. Her background is shrouded in mystery, though it is implied that she was not always the malevolent figure she appears to be. It is known that she was once good and beautiful, and some sources hint that she may have been a former love interest or concubine to King Zarkon before her transformation into an evil sorceress. This tragic fall from grace adds a layer of depth to her character, suggesting a past filled with lost virtue.

Haggar's personality is defined by her unwavering loyalty to King Zarkon, a devotion that sets her apart from other subordinates like General Yurak or even Prince Lotor, both of whom face Zarkon's wrath for their failures. Haggar, however, never seems to incur his displeasure. She is cunning, patient, and deeply committed to the conquest of the universe, using her vast knowledge of dark magic to devise schemes and create terrible weapons. She expresses disdain for Prince Lotor, viewing his romantic infatuations and attempts to impress his father as distractions, though she will occasionally aid him in his plans. Her primary motivation is the service of the Doom Empire, maintaining her power and her crucial role as its chief sorceress and monster-maker.

In the story, Haggar serves a vital role as the architect of the Voltron Force's most formidable challenges. She is most renowned for creating the Robeasts, the giant monsters dispatched to battle Voltron. Her magical abilities are extensive, allowing her to cast hypnotic spells, concoct poisons, unleash plagues, and engage in necromantic schemes, such as violating graves to create clones. One of her most significant contributions to the series' lore is her responsibility for originally splitting the legendary super robot Voltron into five separate Lion components, a key event that sets the stage for the entire narrative.

Her key relationships are central to her role. Her dynamic with King Zarkon is one of absolute fealty, and she is his most trusted confidante. With Prince Lotor, her relationship is more complex; she serves him when commanded but holds him in low regard. She also has a notable connection with her blue, cat-like familiar named Cova, who often assists her in casting spells. As the series progresses into Voltron: The Third Dimension, Haggar's development sees her go into hiding after the final battle of the original series. She later resurfaces to make a deal with Prince Lotor, agreeing to help him conquer the universe in exchange for gaining the magic of the Voltron lions.