In the world of Gegege no Kitarō, Enma-Daiō stands as the formidable sovereign of Jigoku, the Japanese realm of the dead. His principal function is as the absolute judge and ruler of this underworld, a position that places him at the apex of the afterlife's hierarchy. He is the one who determines the fate of souls, deciding the nature and severity of their punishment based on the sins committed during their mortal lives. This role roots him deeply in the broader East Asian and Buddhist traditions of Yama, the wrathful god who presides over the narakas, or hell realms, and the cycle of death and rebirth known as saṃsāra.

Visually, Enma-Daiō is a striking and imposing figure, though his exact appearance has varied across different adaptations of the series. He is consistently portrayed as a giant of a being, often with red skin, wild black hair, and prominent fangs. His attire typically echoes that of a Tang Dynasty official, frequently wearing ornate robes and a distinctive hat that bears the kanji character for King. In some versions, he is shown with horns, and his size is not fixed; he possesses the ability to shift his stature from human-sized to a towering giant, reinforcing his otherworldly power. Despite his fearsome and often angry countenance, this exterior belies a personality that is not entirely malicious. He often speaks with a loud, booming, and sometimes abrasive voice, fitting for a king of his station, but he acts as a force for a certain kind of cosmic order rather than pure evil.

Enma-Daiō's personality is largely defined by his role as a judge. He is consistently shown as a stern and impartial arbiter of the dead, observing the living world to pass judgment. In some interpretations, he is known to dispatch yōkai as his agents to eliminate particularly evil humans, demonstrating a direct hand in maintaining a moral balance. His motivations are tied to the proper functioning of the afterlife and the cosmic order; he is a guardian of the cycle of reincarnation, ensuring that evil is punished and that the world of the living is not unduly corrupted. His role in the story often sees him as a figure of immense, almost untouchable authority. He provides a sense of scale to the world's mythology, representing a power that even the titular character, Kitarō, respects. He may intervene in major conflicts, especially those threatening the barrier between the living world and Jigoku, though he is wary of fighting in the human realm himself due to the catastrophic damage his divine powers would cause.

Key relationships for Enma-Daiō are primarily defined by his position. He rules over the demons and entities of Jigoku and communicates directly with yōkai, sometimes appearing to them as a giant, hologram-like visage in the sky or in their dreams to deliver warnings or orders. While his primary role is static as the King of Hell, his development is subtle, adapting to the tone of different series eras. Across all appearances, he remains a constant pillar of the supernatural world, a figure whose authority is rarely questioned and whose power is immense. His abilities are vast and godlike, befitting the ruler of Hell. He can single-handedly support the weight of all Jigoku and has mastery over reincarnation, able to manipulate the rebirth of souls. His powers extend to the physical world as well; his anger can summon thunderclouds and torrential rain. In combat, he is a devastating force, capable of emitting destructive beams of energy from his eyes and wielding Jigoku's Ultimate Secret Art, a technique that allows him to unleash the full power of hell without any magical key, enough to annihilate entire legions of enemies in an instant. In later adaptations, he has also been seen summoning a naginata, a traditional Japanese polearm, for use in battle.