Without any love for Humanity and with an indifference to life, Poseidon is the embodiment of what defines a God. Due to his cruelty and enormous power, he is called the "Most Fearsome God" (最恐神, Saikyō-shin) and "The God of Gods" (神の中の神, Kami no naka no Kami, G.O.G) by his fellow Gods.

He rules all oceans with an iron fist, earning him the titles of "Tyrant of the Seas" (大海の暴君タイラントオブオーシャン, Tairanto obu Ōshan, lit. Tyrant of the Ocean) and "Zeus Enalios" (海のゼウスゼウス・エナリオス, Zeusu Enariosu, lit. "Zeus of the Seas"); his older brother, Hades, has also referred to him as the "King of the Seas" (海の王, Umi no Ō).

Poseidon takes the form of a tall and muscular man, his face usually completely apathetic and devoid of any emotion, with golden-blonde hair as well as light blue irises and black pupils. He donned an ornamental patterned golden choker and dark blue clothing with a golden border that covers the entire upper half of his body, revealing his abdomen and chest. Around his biceps, he wore a pair of golden rings. Poseidon wore a pair of seaweed-colored fingerless gloves, with a blue band on his wrists, whilst around his waist was a white waistcoat with golden circular patterns, one which split in two at the front with a single cloth going down like a loincloth. Additionally, beneath the waistcoat were a pair of baggy pants that matched the cloth on his arms, tucked into a pair of seaweed-colored boots with designs similar to those of ancient ruins in the ocean depths. He was always seen carrying around his primary weapon, a highly stylized trident as long as his body. Poseidon is a fearsome, haughty, and cold-hearted individual. Like many other Gods, Poseidon despised Humanity and considered them nothing but filth. Poseidon is also a very taciturn and arrogant individual, viewing himself as perfect, saying that he doesn't need any supporters, even calling other Gods "useless bottom feeders" after glaring at them, insulting his older brother and later Kojiro Sasaki, even bitterly cursing him with his last breath as he died. His personality is what Hades believes makes Poseidon the person most worthy of the title of "King" more than any other God, even more than himself. Despite his cold exterior, Poseidon does possess some emotion, especially when it comes to his brothers. Though he dealt him a fatal wound, Poseidon chose to let Adamas live and didn't mind when he was healed by Beelzebub and continued living under a different name in Helheim. Poseidon also seems to care for his eldest brother, Hades; after witnessing Hades defeat the Titans by himself in order to protect his younger siblings, Poseidon uncharacteristically smiled and called Hades "Brother", which he'd never done before. Even before seeing this, Poseidon expressed worry for Hades when he heard his brother went down to Helheim alone to deal with the Titans. This love also extends to Adamas, choosing only to cut him in half and letting Hades and Hermes retrived the injured god for surgery. Poseidon is considered to be the most fearsome among the Gods, so much so that even other Gods were afraid of invoking his wrath. He effortlessly defeated and mortally wounded the God of Conquest and his older brother, Adamas, in a single blow. He's a son of Kronos and a possible participant of the Titanomachy, having complete control over the ocean and being powerful enough to be compared to the Supreme Greek God, Zeus. Poseidon possesses phenomenal physical strength, displayed when he effortlessly impaled a God and even flinging him across the room with so much force that a large indent was left on the wall with nothing but a swing with his trident. Poseidon's strength was further demonstrated throughout his fight with Kojiro Sasaki with each and every one of his swings capable of impaling and annihilating Kojiro. Poseidon managed to break Kojiro's divine weapon in two effortlessly and was even strong enough to crush his own arm. Poseidon displayed unfathomable movement speed, shown when he deflected and dodged all of Kojiro Sasaki's sword swings effortlessly. As the battle progressed, Poseidon started moving more seriously, his speed easily being able to overwhelm Kojiro, moving faster than he can anticipate or register. His trident techniques are also so fast that they create afterimages. Poseidon possesses godly stamina and endurance, cutting him all across his body, Poseidon remained calm and didn't even seem fazed in the slightest. Poseidon's immense pain tolerance was also demonstrated when he continued to fight on, even after losing both his arms, only being put down after finally being quartered by the wandering swordsmen's final attack. Poseidon wields his trident with godly skill and proficiency, being able to deliver dozens of blows in the blink of an eye. He also displayed great dexterity in utilizing his trident in combat, delivering powerful blows incessantly and accurately. Similar to Adamas, Poseidon appears to be capable of materializing his weapon out of thin air. As a God, Poseidon possesses physical abilities far greater than any ordinary Human. His body can not be harmed by mortal weapons. However, he can still be harmed by unarmed attacks from individuals with superhuman strength and Divine Weapons. As a God, Poseidon is incapable of dying due to old age. He is very ancient, being older than the Big Bang (making him over 13.8 billion years old). You and him were born in the same year, except him being older than you by a few days. As the "God of the Seas", Poseidon possesses absolute control over divine water.