Sea Leopard is a Lemurian from a telepathic sect known as the Ancients that resided in Antarctica. The Sea Leopard came into conflict with Namor the Sub-Mariner over the contents of a sunken ship called the Endurance.
Sir Ernest Shackleton led an expedition to the South Pole and landed himself in a place called Palmer Land where he discovered a mysterious ore that caused metals to liquefy. Shackleton and the crew loaded the ship with the anti-metal for roughly about 281 days until the large quantities of metal began to melt the metal structures on the ship. Shackleton and his men abandoned ship and the Endurance sank underneath the ice. Sea Leopard then found the sunken ship and tried to keep the valuable ore as his property.
Phoebe Marrs explained to the Sub-Mariner that she had also sent another expedition to look for the Endurance as well. Namor warns Phoebe that expedition is in danger because Attuma and his barbarian horde were residing within the city of Old Atlantis near the Endurance's location.
Namor and Andromeda travel to Antarctica to stop Leon McKenzie from recovering the contents of the ship. Andromeda travels to Old Atlantis and calls out her father Attuma. Attuma appears from the shadows but collapses in front of her, it is then revealed that he was taken down by Sea Leopard. Namor finds the ship but the Sea Leopard appears holding the bodies of Andromeda and Attuma.
Namor then launches towards the Sea Leopard, who used to telepathy to predict Namor's next move in the battle. Namor tries to use his own telepathy to control a Killer Whale to drag him down into the icy depths.
Then Leon McKenzie who was then disguised as the Black Moray found the ship, but was also approached by the Sea Leopard. Black Moray's suit was able to block Sea Leopard's telepathy so as a compromise he tells McKenzie that he can get the anti-metal as long as he can make Namor to bow down and work for him as his lifelong slave
Attuma and Andromeda then awoke and attacked the Sea Leopard themselves while Namor confronted Black Moray. During the battle with Namor, Black Moray set off a giant explosion on the ship. Sea Leopard beat Attuma and his daughter in combat again. Black Moray tells the Sea Leopard that the ship was destroyed and Namor had been killed.
It was then revealed that Namor was wearing the Black Moray's suit and was able to get close enough to Sea Leopard to strike him. Andromeda and Attuma then help Namor in take down Sea Leopard. Attuma tells Namor that his barbarians would find a suitable punishment for Sea Leopard.
Sea Leopard would appear sometime later with the Fathom Five. In an attempt to destroy all surface life the team attack New York. They attack and lash out any one they meet in the streets. The Thunderbolts counteract the team and after a long battle are defeated and retreat into the ocean. 
The team was defeated and Llyron was nearly killed by the Radioactive Man. They escape and returned to Atlantis, only to discover that he had radiation poisoning, and furthermore, had spread the poisoning among the Atlantean population.
Powers and Abilities
- Telepathy: Sea Leopard has some telepathic abilities. He can probe the minds of anyone in close proximity and predict their movements.
- Homo Mermanus Physiology: Sea Leopard possesses the conventional attributes of Homo Mermanus: gills that extract oxygen from water, superhuman physiology to withstand extreme pressures and temperatures, and acute vision. He can swim at approximately 30 miles per hour. He can remain out of water for approximately nine minutes before beginning to suffocate. However, he can operate on the surface by wearing a water-filled helmet or using a chemical that enables him to draw oxygen from the air.
- Claws and Prehensile Tail: Sea Leopard also has claws on his hands and a tail he can use to strike his opponents with a powerful blow. Sea Leopard's tail is strong enough to snap the spine of small cetaceans and sharp enough to puncture a person's body.
- 5 appearance(s) of Sea Leopard (Earth-616)
- 1 mention(s) of Sea Leopard (Earth-616)
- 2 image(s) of Sea Leopard (Earth-616)