The weed of crime bears bitter fruit. Crime does not pay. The Shadow knows!
The job of actually creating The Shadow went to Walter Gibson, a newspaper writer and stage magician who was a personal friend of (and ghost writer for) the likes of acclaimed magicians Joseph Dunninger, Harry Houdini, and Blackstone. Gibson had an idea for a character with villainous traits, but who was actually on the side of the law. Originally conscripted for merely the first four stories, Gibson went on to write not only the vast majority of the pulp series, but also episodes of the radio series (which began in 1937), Street & Smith's Shadow Comics, and the Shadow newspaper strip.
Naturally, countless imitations sprang up in the pulps - The Spider, The Phantom Detective, and The Black Bat - not to mention the comic book superheroes The Shadow inspired such as Batman (and much more recently, Francesco Francavilla's Black Beetle, which I highly recommend). However, none of these other pulp series lasted as long as The Shadow himself - The Shadow Magazine was uncontested as the longest running pulp hero series in history. Doc Savage's series lasted for 181 issues, and The Phantom Detective only made it to 170. Even the Lone Wolf, hero of the Western pulp Texas Rangers, only reached 212 stories.
Still, there were a few villains that took more effort (and more than one book) to put down for good. Crooked lawyer Isaac Coffran showed up several times in the earliest novels, as did his henchman Steve Cronin - while Cronin was killed off in the fifth novel, The Shadow never had a showdown with Coffran, although Gibson supposedly planned one. However, more formidable recurring foes were to come. The first of these was Dr. Rodil Mocquino, AKA The Voodoo Master, the first Shadow villain to make a reappearance after seeming death. The Voodoo Master lasted for three stories, meeting his final end in the third. Theodore Tinsley came up with another recurring for The Shadow - Benedict Stark, the self-styled Prince of Evil, an uber-wealthy criminal mastermind who simply enjoys being evil, and who stuck around for four installments. A less successful attempt at another recurring villain was The Wasp, who only lasted for two stories. A five-part series pit The Shadow against a quintet of racket leaders known as The Hand, who operated separately across the United States.
Much to my surprise, I actually got a reply from them - and the content of said response was an even bigger surprise: "we're working on it."
And they were.