U-Man

The character Meranno first appears in the title Invaders, and like hero Namor the Sub-Mariner is a member of the Atlantean race, Homo mermanus. It is revealed in flashback that Meranno despised Namor when they were children, and in adulthood allies himself with Nazi Germany. Still consumed with hatred for Namor, the character reveals the location of the city of Atlantis to the German forces, who destroy the Atlantean fleet and place the then Emperor Thakorr in a coma. Thakorr is succeeded by Namor, who banishes Meranno from Atlantis for treason.

Meranno adopts the alias of U-Man, and willingly submits to Nazi procedures that increase his size and strength. Joining a fleet of U-Boats, U-Man wreaks havoc on the Allied fleet until defeated by the superhero team the Invaders. The character reappears in a two part story in the title Marvel Two-In-One, and with Nazi allies Brain Drain, Master Man and Skyshark plans to sabotage New York City with a new super weapon. The plan, however, is foiled by time travelling Fantastic Four member the Thing and the Liberty Legion.