Marvel’s first character debuted in a special promotional called Motion Picture Funnies in April 1939. Creator Bill Everett repackaged the story and added new pages to fit the format Martin Goodman had in mind for Marvel Comics #1 in October 1939.
He was Marvel’s first hero (technically, the original versions of The Human Torch, Ka-zar, and the Angel appeared in Marvel Comics as well, but Sub-Mariner was created before this issue and maintained much of his continuity since then.)
He was the first flying hero in comics, flying in both of his first two adventures and drawn with tiny wings on his feet – his mutant ability. His flying predates The Human Torch who leaps in his first two appearances, Hawkman (Jan 1940), or Shazam’s (June 1940) first flights who all flew before Superman did in 1941. Namor was involved in comic book’s first crossover (Marvel Mystery Comics #7-10, including #9’s 22-page “Battle of the Century”) with The Human Torch. They had several crossovers in their first three years, with the most well-known being in the epic 60-page tale in The Human Torch 5(b), Fall 1941 “The Human Torch Battles the Sub-Mariner as the World Faces Destruction.”
The Sub-Mariner was an anti-hero from the beginning, brutally killing two divers in his first appearance. He ran amok in New York City several times, starting with Marvel Mystery Comics #2, but also saved a British ship from a Nazi sub. New York tried and convicted Prince Namor (no diplomatic immunity for the denizens of the deep). Namor was sentenced to the electric chair in Marvel Mystery Comics #6, but as a lethal jolt was sent into his body, the drug they were using to subdue him was rendered inert. He broke free, as powerful as ever, and escaped. In issue #4, he kidnapped police officer Betty Dean and tried to keep her on the bottom of the Southern Ocean with him in his stronghold. The Sub-Mariner was also comic’s first biracial character as his father was American Leonard McKenzie and his mother was Princess Fen, who lived in an undersea kingdom located off the Antarctic coast. He had abilities beyond the races of either parent. In the Golden Age, Sub-Mariner appeared in every issue of Marvel Mystery Comics until #91, one issue before it was retitled as the horror anthology Marvel Tales. He also appeared in a secondary feature length story in The Human Torch from #1-33 until just before it ended publication with #35, All-Select 1-5 & 10, All-Winners 1-19, 21 and the relaunched #1, Blonde Phantom 13-15, 17-22, Namora 1-3, Captain America Comics 20, 68, 70, Daring 9-12, and Sub-Mariner Comics 1-32. That’s over 200 comics. Many of the quarterly and the three Namora issues had 2 full-length oceanic epics. That’s not even including the relaunch in the Atlas era, which had another 50 tales to tell. That’s about 280 stories of the Avenging Son before Fantastic Four #1 ever saw print!
The Avenging Son had the privilege of being drawn by one of the Golden Age’s most talented artist/writers, Bill Everett (series creator). Most of his cover appearances are illustrated by the incomparable Alex Schomberg (who also did pencils on the first story in Sub-Mariner #3, though it’s not nearly the same quality as his cover work.) After Bill Everett went off to serve his country, Carl Pfeuffer took over for a few years. He’s a very underrated artist that got a bit crazy with how extreme he evolved Namor’s head in to a wedge shape. I was really hoping Marvel would print more of his work. Namor was also a founding member of Marvel’s first superhero team, the All-Winner’s squad. Namor was the first golden age character introduced into the Marvel Age. Namor was also a founding “member” of the first non-team superhero team, the Defenders and was a founding member of the first retro superhero team, the Invaders. Namor’s Golden Age tales are partially collected in Marvel’s Masterworks program. Marvel Mystery Tales Vol 1-7 (4 giant-sized issues each), the complete All-Winners Vol 1-4, Sub-Mariner Vol 1-3, and The Human Torch Vol 1-3. I would recommend the Marvel Mystery Omnibus, which has the latest restoration and a lot of extras. For The Human Torch, All-Winners and Sub-Mariner Vol 1, softcover Masterworks are the best bet. Not only are they easier to find, but they have better quality restorations. I was hopeful that Marvel would do a Vibranium Edition or omnibus Sub-Mariner collection to celebrate the 76th year since he debuted.