Poseidon stands among the Greek Pantheon's major deities within the *Record of Ragnarok* universe, revered as the God of the Seas and known to his divine kin as the "Most Fearsome God" and the "God of Gods" (G.O.G.). He is the third son of the Titan Kronos, brother to Zeus, Hades, and Adamas.

Born before the Big Bang, Poseidon exceeds 13.8 billion years in age. His existence consistently displayed profound indifference toward Adamas, ignoring him completely even when directly addressed. This starkly contrasted his respect for his eldest brother, Hades, whom he aided during the Gigantomachy and Titanomachy. Witnessing Hades single-handedly defeat the Titans in Helheim prompted Poseidon to smile uncharacteristically and address him as "Brother" for the first time, acknowledging Hades' worthiness as a king. Following these conflicts, Poseidon ascended as the undisputed ruler of the oceans, earning titles like "Tyrant of the Ocean" and "Zeus of the Seas."

His reign embodied absolute authority. When Adamas orchestrated a coup against Zeus, Poseidon confronted him, condemning his reliance on alliances and scheming as violations of divine perfection. Poseidon delivered a single, mortally wounding strike but permitted Hades and Hermes to retrieve Adamas for healing, motivated solely by preventing Hades' grief. Adamas later resurfaced in Helheim under the name Adamantine.

Physically, Poseidon manifests as a tall, muscular man possessing golden-blonde hair, light blue irises, and a perpetually apathetic expression. His attire comprises a dark blue garment edged in gold, a golden choker, spiked golden arm rings, seaweed-colored fingerless gloves and boots, and a white waistcoat adorned with gold motifs. He wields a stylized trident as his primary weapon, materializing it at will.

Poseidon's personality is defined by profound arrogance, emotional detachment, and an unwavering belief in divine supremacy. He perceives gods as inherently perfect beings requiring no peers, support, or collaboration – a philosophy he reiterated during his duel with Kojiro Sasaki. He holds humanity in utter contempt, considering them insignificant. Despite his pervasive coldness, he harbors genuine loyalty to Hades, evidenced by his sparing of Adamas.

In combat, Poseidon possesses godly physical attributes: immense strength enabling effortless shattering of divine weapons, blinding speed creating afterimages with trident thrusts, formidable endurance allowing unimpeded fighting after severe injuries, and semi-immortality. His trident mastery enables techniques like *Amphitrite* (blindingly fast circular thrusts), *Chione Tyro Demeter* (a lightning-resembling aerial barrage), and *Medusa Alope Demeter* (omnidirectional strikes forming a dome of afterimages). As God of the Seas, he demonstrates hydrokinesis, parting water with a footstep, though he never employs this ability offensively.

During Ragnarok's third round, Poseidon represented the gods against the human swordsman Kojiro Sasaki. Initially dismissive, he escalated his speed and ferocity as the battle progressed, overwhelming Kojiro's predictions. Despite breaking Kojiro's weapon, Poseidon was ultimately outmaneuvered and quartered by Kojiro's perfected technique. With his final breath, he cursed his opponent before being banished to Niflhel.

His techniques' names reference Greek mythological figures associated with him: Amphitrite (his consort), Chione, Tyro, Demeter (his sister and one-time lover), Medusa, and Alope.