Karl was born a Saxon, but as an infant his father died fighting Viking raiders. Impressed by his fallen foe's bravery, the Viking leader adopted the man's infant son as his own and raised him to be a mighty Viking. An honorable warrior, after he became a chieftain, Karl led his men on adventures across the world, from what would one day be called America to Egypt and even Atlantis.
Created by artist Don Lawrence and writer Ken Bulmer, Karl the Viking debuted in Lion on 29th October 1960 in the strip Sword of Eingar, which saw chieftain Karl and his rival Skurl both having pledged to recover the eponymous weapon stolen by a Saxon lord, Earl Gyrth of Eastumbria. The hero's popularity resulted in the strip continuing after the end of this initial quest, now retitled Karl the Viking. It ran for four years, ending on 29th September 1964, with a total of thirteen adventures spread across 205 episodes, plus four more in the Lion Annuals, one of which was written by Michael Moorcock. Lion replaced Karl with English crusader Maroc the Mighty.
In the British comics business, it was a commonly held belief that the teenage readership would grow out of comics and be replaced by a new audience every five or so years, on 1st October 1966 Lion began a series of reprints of Karl's early adventures, though he was renamed Rolf to engender the impression that this was a new strip, which they titled Swords of the Sea Wolves. Rolf's adventures ended after a year, on 7th October 1967, though not before Lion Annual 1968 carried a brand new adventure. Two years later Karl enjoyed another reprint, this time in Smash!, where he reclaimed the title of the strip under his new name, Erik the Viking. Erik appeared in Smash! between 3rd May 1969 and 3rd April 1971, and had a new text adventure in Valiant Summer Special 1971 (after Smash! merged into Valiant).