In 1970, Jack Kirby left Marvel Comics to work at DC Comics, where he began the saga of the New Gods, an epic story involving mythological and science fiction concepts, and planned to have a definite ending. However, the saga was left incomplete after the cancellation of the titles. Kirby then began working on The Eternals when he returned to Marvel. The Eternals' saga was thematically similar to the New Gods', and the series was also eventually canceled without resolving many of its plots. Writers Roy Thomas and Mark Gruenwald used the Eternals in a Thor storyline that climaxed in Thor #301, resolving those lingering plotlines. Subsequent to the Thor storyline, the Eternals (and the mythology connected to them) have appeared or been mentioned in numerous Marvel comics. In particular, the Celestials' experiment on humanity has been used to explain how certain humans can develop super-powers. The Titanians (created by Jim Starlin) and Uranians (created by Stan Lee) were later retconned as being Eternals as well.