Before her Meta-Gene activation, Delphis was an olive-skinned teenager with black hair and brown eyes. Her hair was slightly curly, and reached to her waist.
Post-transformation, her eyes turned pale blue, while her hair turned white. She gained bright blue markings all over her body. She also gained visible gills and webbed hands.
The girl who would come to call herself Delphis had a difficult and traumatic life, which she is extremely reluctant to discuss. She knew many bad men, and spent some time in Mumbai, where she experienced the difficulties caused by economic inequality.
The young girl was abducted and trafficked to an abandoned factory in Cuba, where Klarion activated her Meta-Gene with his sorcery and applied a mystic control brand to her forehead. Seeing no practical use for a meta-human who could not breathe on land, Klarion turned her into mist and combined her essence into an amalgamation of writhing flesh. Upon her assimilation, the flesh monster developed gills.
After Zatanna defeated the flesh monster and freed all the kidnapped meta-teens from Klarion's brand, Beast Boy heard her suffocating. Seeing her gills, he realized she couldn't breathe air and quickly brought her underwater. He summoned the Bio-Ship and nudged her towards a compartment inside.
After dropping off the trafficked meta-teens at the Meta-Human Youth Center, Beast Boy showed Aquaman the "special case". Aquaman noted that the center was not equipped for water-breathers and that alternate arrangements would have to be made.
Upon arrival, Aquaman cast a translation spell so that she would be able to communicate with others. She was introduced to King Orin. Aquaman also introduced her to his parents, Calvin Durham and Sha'lain'a, who would help her adapt to Atlantis. Calvin was from the surface himself, so he could pass on his own experiences to the young girl.
Delphis and Sha'lain'a waited outside the annual conference of city states. When Kaldur and Wyynde came out, Delphis suggested they show her around Poseidonis. As they swam around the city, Delphis noted the relative splendor of Poseidonis compared to Shayeris, leading to a discussion of the inequality in Atlantis. Wyynde said they should save the politics for the conference and suggested they visit an algae bar. Wyynde ordered the group some Black Gold, which Delphis enjoyed, and Kaldur introduced her to Lori Lemaris, who greeted her warmly, but was far colder to Wyynde. A fight broke out when Nanaue Sha'ark arrived and taunted Lori, but Kaldur calmed it.
Delphis stayed nearby during the second day of the conference, and rushed in when Ocean-Master attacked. She used her light power to dazzle Ocean-Master, preventing him from blasting Kaldur, and joined the group assault on him. Ocean-Master easily overcame his attackers, but was stopped by a mysterious stranger with great magic powers.
In the weeks following the attack, Delphis helped those displaced by it.
At Kaldur and Wyynde's home, Delphis and Wyynde discussed her work with those displaced by the attack. Kaldur arrived and told Delphis she was welcome to stay with them to continue her work. She passed on a message from Kaldur's parents, asking him to call them. She and Wyynde then went outside to give Kaldur privacy. They soon called him outside to join them as they witnessed a giant pillar of fire form just outside the city dome.
Delphis stayed with Wyynde at a city gate and watched as Kaldur, Orin, Mera and, later, Ocean-Master fought to quell the pillar. She helped hold La'gaan back when he tried to go out to rescue Blubber. Once the stranger appeared and helped Mera and Orm, the gathered crowd began whispering about a prophecy, to Delphis's confusion. Once the pillar was extinguished, Delphis and other rushed outside the dome. They found Ocean-Master attacking Mera and Kaldur, only to be stopped by the stranger and arrested by Orin. Delphis went to help an injured Kaldur. Once the stranger reluctantly revealed himself to be Arion, the crowd started to chant his name, prompting Delphis to ask Kaldur who he was.
Delphis overheard Wyynde and Kaldur arguing over Kaldur overworking himself. She joined them and asked to join their covert mission for King Orin, but Kaldur denied her, saying she was already busy and not suitably trained.
Delphis followed anyway, and used her light powers to distract a group of Nereus's Watch that nearly caught Kaldur's squad. Kaldur welcomed her to the team, and the group finished the tunnel through the seabed.
The group entered the Undersea, but their tunnel soon collapsed, causing a wider cave-in that forced them to rush forward and drill through another barrier. Kaldur was confident they could dig their way out when they were done, and the group moved on, with Delphis using her power to illuminate the dark cavern.
After a month in the Undersea, the group had not found the crown, but had become adept at finding and dousing the geothermal vents that periodically erupted there. What they initially thought was another geothermal vent turned out to be a giant crab emerging from the sea floor. The group fled, but the crab sucked the group toward its mouth, until La'gaan allowed himself and a pillar of rock to be swallowed. The pillar was distasteful, so the crab spat La'gaan out and moved on.
Delphis saw that the crab had emerged from a chasm, which the group then swam down. They found ruins from the ancient Atlantean capital, and the three magically trained members could all sense great magic power nearby. They fanned out to triangulate its location, and quickly found Arion's crown shallowly buried in the ground. Another giant creature then appeared. Kaldur took hold of the creature and rode it. He then shocked the creature to make it move, as the others grabbed ahold. They rode the creature as it swam upwards, jumping off just before the creature crashed into the ceiling of the Undersea, creating an opening for them to escape through.
They returned to Xebel to find Arion taking the mantle of High King. Before anything else could be said, Arion took the crown and donned it, but was immediately killed by the Lords of Order. Mera then went to crown Orin once more, but Orin insisted that it was Mera who satisfied the prophecy and was the rightful High King.
Later, she relaxed with Kaldur and Wyynde at their home.
Dolphin is an underwater super-hero with extraterrestrial origins who becomes a member of the Aquaman Family. Meeting Aquaman during a battle with Charybdis, the two develop a romantic connection. Following their break-up, she marries Tempest and they have a child named Cerdian.