DC Database

Poseidon is the Olympian and Atlantean God of the sea, earthquakes, horses and storms. He is brother of Zeus and Hades, and uncle of Wonder Woman. Poseidon often serves as a supporting character to Wonder Woman and Aquaman, the latter of which possesses the Trident of Poseidon.

Ancient Times

Seeing how great the ideals of the Atlantean hero Arion were, Poseidon decided to reveal to him a secret; of all the oceans in space, only the one on Earth was rich of the Life Force, a power that the Olympian possessed being the god of the seas. Arion studied a structure called the Conch he developed in Atlantis and broadcasted a message through space, and the Triumvirate of Sea Gods answered, in hope to receive this gift as life on their planet was struggling to develop.

After learning of this, Poseidon was afraid to give his power away, and was selfish; he tricked Arion into believing the gods were evil invaders. So the Atlantean hero reversed his plan and instead put the Tear of Extinction inside himself and the Conch and with it, he gave his life to kill the three alien gods. Since then, Atlantis started its history of reclusion and closure.[1]

The New 52

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This section of the history takes place during the New 52, between the events of Flashpoint and DC Rebirth. It was later revealed that much of Wonder Woman's history from this time was an elaborate illusion created by the Gods of Olympus to keep her away from Paradise Island. All or part of this section may have been part of that illusion and no longer valid in Rebirth.
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Poseidon in the New 52

Poseidon was among those vying for Zeus's throne, and ended up attacking Wonder Woman. He was later killed by the First Born before it was revealed that this version of Poseidon, and his fellow Olympians were fakes created by the originals as part of a plot to manipulate Wonder Woman.

DC Rebirth

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Poseidon as Captain Proteus

Thanks to one of The Seven Forces of the Universe freed by the Source Wall's rupture, the Tear of Extinction, Poseidon was killed by Cheetah using her empowered claws at the behest of the Legion of Doom.[2]

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Poseidon's spirit in the Graveyard of Gods

After dying, Poseidon's spirit was sent to the Graveyard of Gods, where he find Aquaman and Wonder Woman. As the Atlantean asks him to restore his powers, Poseidon pierces Aquaman with his Trident. So, Wonder Woman fight against Poseidon, but seeing Aquaman back on his feet, he feels guilty about his actions.

Poseidon then explains how things really went with the Triumvirate in the past. With the dimension around them collapsing, Poseidon gives his trident to Arthur and then uses the last power he has to send Diana and Arthur away, back home on Earth.[3][1]

Infinite Frontier

Poseidon was possibly resurrected alongside all of the other gods due to the actions of Wonder Woman.[4]