From The Unofficial Guide to the DC Universe:
In a dimension of sword and sorcery, a young boy challenged the might of the Demon Lord Dgrth, won immortality but lost his own soul. Regretting his actions, the heroic young warrior began a seeminlgy eternal quest to regain his lost soul. However, the being, now known as Stalker the Soulless, never accomplished his mission. After millennia of soul-searching and acts of heroism, his mind became dark, corrupt. At the same time, his power increased, and more and more, he looked like a duplicate of Dgrth, his bane. Finally, he decided that the only way to know final peace would be to destroy the universe itself. After causing the destruction of his own realm, Stalker went from world to world, from dimension to dimension, leaving dead heroes, gods, and whole universes in his tracks.From Wikipedia:
In 1945, Stalker was transported to Earth by a group of Nazi occultists who had attempted to summon the diabolic Koth. Absorbing the power of the Spectre, Doctor Fate, and other magic heroes, Stalker began his extermination of Earth. The Justice Society and many of their friends and allies fought Stalker's mind-controlled Nazi Disciples, and later Stalker himself. With the help from Doctor Occult, who sacrificed his own soul to give Stalker one, the menace was thwarted, and Stalker finally knew peace.
STALKER is a 4 issue comic-book series created in 1975 by Paul Levitz (writer), Steve Ditko (penciller) and Wally Wood (inker), and published by DC Comics.
The series takes place on a world that appears epic fantasy-based, but when the protagonist travels to his world's version of the underworld, men in astronaut garb can be seen among the hordes of doomed souls, perhaps inferring that the humans on this world were originally stranded galactic travelers.
A young urchin boy trades his soul with the demonic god of warriors for the skills and toughness to survive this hostile, amoral world. He grows up to be the most deadly warrior to walk the earth, but finds it impossible to enjoy without a soul. He eventually fights his way to the demon god in the depths of hell and defeats him, only to discover that the deity has already used of the energies of the traded soul. The only way to get his soul back would be to end the existence of the god, which can only be brought about by the end of all war.
After the cancellation of the title, Stalker would not appear until the 1990's series JUSTICE SOCIETY RETURNS which cast Stalker as a now insane villain, destroying dimension after dimension in his quest to end all conflict. This notably contradicts Stalker's original characterization as an individual capable of acts of heroism and mercy to even evil opponents despite his supposed lack of a soul.