Marvel had blundered into a real success with Robert E. Howard's Conan the Barbarian. The Bronze Age was blooming and with the now mostly defunct Comics Code having eroded somewhat, the time was ripe for new and old genres to return among the cavalcade of superheroes. Conan was a spearhead in the move for diversity.
But with success the desire to imitate is quickened and so Marvel cast about for a copy of their highly successful (ultimately) sword and sorcery star. Gullivar of Mars and Thongor of Lemuria would be given the nod. But clearly the best first choice was found in Howard's own works, specifically the hero who had preceded and was in many ways exceedingly similar to Conan, the answer was King Kull.
Marvel would eventually give King Kull his own series which twisted and turned with more than a few cancellations for many years. But they tried him out in one of their monster comics. The title had been Tower of Shadows and it had debuted alongside its companion Chamber of Darkness a few years previous as EC-style horror mags featuring new stories and art from the Marvel Bullpen. But that didn't seem to be successful, so the decision was made to turn Tower of Shadows into the Creatures on the Loose and feature reprints of vintage Marvel/Atlas monsters from the classic days.
But during that transition, there had been plans apparently to feature a King Kull story written by Roy Thomas (his second go at the characters as shown here) and drawn by the young turk talent Berni Wrightson.
Wrightson would make his reputation a year later at DC when he and Len Wein co-created Swamp Thing, but at that moment he was doing covers for Marvel, specifically the aforementioned horror mags Tower of Shadows and Chamber of Darkness. Here's a glimpse of his work on these comics.
Wrightson was graduated from covers to a complete story with King Kull.
This story was an adaptation of a Howard story which had only recently been uncovered and published. It speaks for itself, and you can read "The Skull of Silence" in its entirety here.
But what's curious is how Wrightson's original cover for the story was shelved in favor of the Marie Severin version eventually used. Marie's is more kinetic in a classic comic book way, but Wrightson's is the better cover, more obviously in keeping with the story it advertises. Maybe it was the title change that prompted the new Severin cover, as it seems to have been made very quickly, since ads about Kull being in Tower of Shadows had already been published. Maybe Kull's back is too much to the reader, but whatever the cause, the cover was changed and Wrightson's Kull was hidden behind a rather superheroesque cover.
Ah well, it all worked out. Berni Wrightson left Marvel and soon enough was working alongside Conan artist Barry Windsor-Smith and two other young talents, Jeff Jones and Mike Kaluta. These four became "The Studio" and were somewhat like rockstars of comics during the Bronze Age. It's sad that Berni's Kull didn't thrive, but we still have that one great story.