Leron is a major enemy of Mera. Both are natives of Dimension Aqua. Mera was the reigning Queen, Leron the leader of a revolt against her. He managed to depose Mera, but not to capture her. Xebel, chief scientist in her service, transferred the queen to another dimension, that of Earth (Earth-1). Uneasy on his throne, Leron was forced to pursue her there. He found her in the company of Aquaman, Aqualad and Quisp. He used his powers to defeat and capture them all, bringing them to Dimension Aqua. But Arthur discovered the weakness of the residents to a common Earth element, lead. A weakened Leron was unable to prevent all prisoners from escaping back to Earth.
Leron was not actually defeated. Mera soon settled with Aquaman in Atlantis, posing no real threat to his rule. He ruled peacefully for a few years. but then Mera returned. Her son, Arthur Curry, Jr, was sick. She needed a healing device of her dimension. But Leron had discarded all the leftover technology of her reign. The two rival rulers faced each other in a hard-water combat. But Mera had practiced her powers for several years while Leron had been idle. She easily overwhelmed him. The strain of the battle shattered Leron's mind. He was last seen in a vegetative state.
Leron shares several powers with Mera and other members of their race. Their world is covered entirely in water and their race are amphibians. Swimming is their equivalent to walking. Their main power is hydrokinesis. They have the ability to psionically increase the density of volumes of water and shaping them to create hard-water constructs. He can use them to cause blunt force damage or simply drown opponents. He has low-level telepathic powers, allowing him to communicate with others. He can not perceive the thoughts of individuals not broadcasting to him. His main weakness is common to all his race. Lead causes them to loose their hydrokinetic powers for the duration of their exposure to it.