History
Sub-Mariner seemingly had the same history as his Earth-928 counterpart. He would go on to join the vigilante group known as the Defenders.[1]
Avengers[]
While their teammates were in a quarrel with the Avengers, Roman and his girlfriend Valkyrie, captured both teams' intended target, Martin Hargood. When everyone else caught up, Hercules started flirting with Val, but Roman got jealous. The two engaged in a brawl, but was stopped by Silver Surfer. Cooled down, the teams brought Hargood to be interrogated at Alchemax Tower. While the teams were getting to know each other, the two almost fought again, but Hawkeye suggested they have a drinking contest instead.[1]
Drunk, Roman was bonding with Hercules when Alchemax guards came to arrest him. Unbeknown to him, Alchemax CEO Miguel Stone had declared the Defenders outlaws. Evading the guards alongside Herc, the duo regrouped with Captain America and freed Hulk and Surfer before escaping the tower.[2]
Meanwhile, Hargood had escaped from confinement and had summoned the Dweller-in-Darkness. Miguel called them, allowing them to intervene without being arrested. After Captain America defeated Hargood, Roman pitted Giganto against the Dweller. Giganto was able to inflict enough damage to allow Strange to send the Dweller back where it came from. Later, he was present when Miguel undeclared the Defenders outlaws.[3]