Poseidon is the Olympian god of the sea and the brother of both Zeus and Hades. Poseidon is one of the more vengeful deities, as proven when Cecrops selected Athena over Poseidon as the patron deity of Athens, Poseidon then cursed Cecrops to roam the seas for eternity, though Athena blessed him with immortality so that he could find a way out, (which he did) (XWP "Lost Mariner").
Poseidon also cursed Ulysses while the hero was on his voyage home from the Trojan War. Ulysses was aided by Xena and Gabrielle (just like Cecrops) and eventually prevailed against the sea god (XWP " Ulysses").
He is the father of Triton, Antaeus, as well as Polyphemus (in the myths he was the father of many others, but none were ever featured). He is technically the first deity to appear on Xena: Warrior Princess, as he appears briefly in the opening sequence when the narrator mentions "ancient gods".
Powers and Stats
Tier: 7-B, likely far higher
Age: Unknown, many millennia old at least
Classification: Olympian God of the Sea
Powers and Abilities: Super strength, speed, and durability, Immortality (type 4), can give immortality or take it from lesser beings, enhanced senses, Logia Intangibility, Shapeshifting, manipulation of the seas and weather, Fate Manipulation (cursed Cecrops to never be able to return to land until love redeems him), Creation of monsters such as Charybdis, Time Manipulation of various forms (can stop time, travel through time, BFR others through time, loop time, and is immune to time stops), Soul Manipulation, Mind Manipulation, Telekinesis, Illusion Creation, Matter Manipulation, Petrification, Dimensional manipulation, Can open portals to other dimensions, and with assistance, other universes, Reality Warping
Attack Potency: At least City level, likely far higher (Used his powers to give Nautica a heart that can warm or cool the oceans)
Speed: Subsonic+ reactions via powerscaling
Lifting Strength: At least Class 25
Striking Strength: At least Unknown
Durability: At least Building Level due to his sheer size, immortality and intangibility makes him hard to kill
Stamina: Essentially limitless
Standard Equipment: His trident
Intelligence: Many eons of knowledge as an immortal god
Weaknesses: Has never been shown to be able to operate away from water