Orin was the ruler of the Atlantean city of Poseidonis in the years prior and immediately following the Great Deluge. Most regarded Orin as a strong and benevolent leader, but there were those, including his brother, Shalako, who felt that Orin's compassion made him a weak ruler. Orin was the first to put together the Atlantis Chronicles and assigned Albart-Son-of-Yarrow of Ancinor the task of maintaining a faithful history of their home country.
Orin was a technocrat, whose advances in science helped to propel Atlantis to a new golden age. There were those though that felt that Orin's greatest blunder was his endeavoring to share his works with other cultures. He visited nomadic tribes and taught them how to make rudimentary weaponry of tempered steel such as swords and spears. He also taught them how to hunt game with bows and arrows. He never considered that this knowledge could somehow be turned against him.
As it is though, those who benefited from Orin's graciousness turned against him. Barbarian tribes from outlying settlements would lay siege to Poseidonis, killing scores of people. Orin always tried to keep the peace, but some of his policies were deemed too soft in light of the violence that had been visited upon them. At one point, the leader of one of the barbarian hordes, visited Poseidonis with an offering of peace and Orin accepted him as his word. This did not mean that Orin was blind to the threat that these nomads still represented, and so he commissioned the construction of a great dome to surround the city. Made of pumice stone, the dome was translucent, and porous enough to allow for light, air and water to get in, but was strong enough to withstand physical bombardment. The construction of the great dome was met with both praise and lamentation. Orin's brother, the priest Shalako, believed that cutting Poseidonis off from the rest of the world was an affront to Suula - Goddess of the Sky. Though Orin respected the traditions of the gods, he felt that practicality overruled their judgment. Shalako, as well as Orin's seer, Rajar, both warned him that dark times lie ahead for all of Atlantis.
It would seem that Suula's vengeful wrath would in fact come to pass. Rajar had detected a massive skull-shaped meteor in outer space on a direct course for Earth. He knew that if such a massive celestial body struck the planet, it would mean the end of everything. At first, Orin scoffed at Rajar's concerns, but when it became apparent that the threat was real, he ordered his men to use a massive laser cannon to destroy the meteor before it could enter Earth's atmosphere. In order to properly target the meteor though, they had to move the cannon into the territory of the barbarian hordes. Orin sent Rajar as an emissary to ask permission to set up their cannon in their lands. The savages responded by beheading Rajar and sending his head back to Atlantis on a pike. Orin was incensed and ordered his soldiers to kill the entire barbarian tribe.
They eventually set up their cannon and fired it at the meteor, but discovered to their eternal horror, that it had no effect. There was nothing they could do. Orin prayed that the dome surrounding Poseidonis would be strong enough to withstand the impact of the meteor. The meteor soon struck the Earth, causing worldwide geological upheaval. The tectonic plates shifted and all of Atlantis sank beneath the waves. As Orin had hoped, the dome surrounding the city protected them, but they could never again leave the city. 
Some saw Orin as the savior of his people for constructing the dome. While others, including Shalako, condemned him for bringing the wrath of the gods down upon their heads. Orin tried to maintain the peace as best he could, but after only a few short years living beneath sea, civil unrest began to tear Poseidonis apart.
Orin consulted with his chief scientist, Thorne, who had been working on a method to turn air-breathing humans into amphibians. Orin did not wish to give the people of Poseidonis false hope, so he made sure to keep Thorne's work a secret. Once a serum had been perfected, Orin insisted on being the first volunteer to test it. The serum proved to be a miraculous success and Orin's adapted to the changing pressures of the ocean. He was able to leave the domed city and draw oxygen from sea water as if he were breathing normal air. Once the experiment was deemed a success, he quickly administered it to everyone in Poseidonis.
Orin and his entourage then went to visit his brother and his followers, who had since migrated to the ruins of nearby Tritonis. He showed them that the could now live outside their respective domes, and offered the serum to anyone who wished for it. The Shalakites of Tritonis flocked to Orin's side, thus enraging Shalako, who took their acceptance of Orin's work as a personal betrayal. He cursed his own people, transforming them into a race of scaly, mer-people. Orin watched in horror as his brother's followers then turned their leader, killing him. The crazed Shalakites sought out and destroyed anything having to do with Shalako. Only Dardanus (Shalako's son) was saved. 
As time passed, Orin discovered that the serum that had made him amphibious was producing some unexpected side effects. It had slowed the aging process and it was becoming more and more difficult to process oxygen. He came to realize that the only way he and the other Atlanteans could survive were if they were to live permanently in the sea. He opened the flood gates to the great dome, allowing tons of water to fill the city. The people of Atlantis survived of course, but they now had to adapt to living as a pure undersea race.
By this time, Orin's daughter, Cora, had become the Atlantean head of state and he felt that it was finally time to step down as Monarch. At a public coronation, he announced that Princess Cora would now serve as the new Queen of Atlantis with her husband Bazil serving as Warlord. Orin continued to serve the throne, but only in an advisory capacity. Cora's first act as Queen was to announce her daughter, Fiona, as the heir to Atlantis. Kordax suddenly appeared, publicly challenging the decision. By right of birth, it was he who should inherit the throne, not Fiona. The scandal causes heated tension between those who supported Princess Fiona's right to ascension and those Tritonians who sided with Kordax. Before long, both city-states went to war. 
Orin and Bazil led Poseidonis' forces during the war between Poseidonis and Tritonis. Subsequently, Orin fought to the death against his nephew Dardanus. Suddenly, the spirit of his dead brother Shalako appeared. With Orin distracted by Shalako's magical spirit, Dardanus plunged his sword through Orin's heart from behind, killing him. Shalako then killed Dardanus. After the death of Dardanus, the magical spirit of Orin arose and defeated the spirit of Shalako.
Orin was laid to rest in a great but sad ceremony. 
- Atlantean Biological Adaptation: Due to the scientist Thorne's experiments, Orin was granted the ability to endure the pressures of the deep.
- Amphibious: Due to the scientist Thorne's experiments, Orin was granted the ability to breathe underwater and survive the increased pressure of the ocean depths.
- Aquaman's birth name is Orin. He was named for his ancient ancestor.
- Although Atlanteans of Orin's time typically had multiple wives, Orin only took one bride - Narmea. It has been suggested, though never proven that Orin may have carried on an affair with a woman named Gulacia. By his own assertion however, Orin holds that he has always been faithful to his wife.
- 7 Appearances of Orin I (New Earth)
- 15 Images featuring Orin I (New Earth)
- 2 Quotations by or about Orin I (New Earth)
- Character Gallery: Orin I (New Earth)