Sin-Dar was a statesman from the city of Kandor on the planet, Krypton. In the Kryptonian year 9852, citizen of both Kandor and the devastated Kryptonopolis were still suffering from hardships left behind by the Last War. Several diplomats, including Sin-Dar, gathered together in an effort to formulate a united federation of Kryptonian city-states and draft a new constitution. Sin-Dar suggested that Krypton should be governed as a democracy with elected officials, judges and lawyers. His colleague Hal-Vu however, recommended that new Kryptonian leaders should be chosen by lot, while the scientist, Tala-El, preferred to see Krypton ruled as a technocracy.
Unable to reach a decision, Tala-El elected to consult with his uncle, Yu-El, a priest of Rao. He asked Yu-El to arbitrate the dispute between himself and the other councilors. Yu-El exclaimed that only Rao could ultimately decide on Krypton's future. He posed a contest wherein the four delegates would gather on the Plain of Wanan outside the city of Kandor to wait out an approaching thunderstorm. Each delegate would carry with him a lightning rod, and whoever's rod was not struck by lightning, would lead the deciding vote for the federation.
Sin-Dar and the others did as instructed, and brought their respective lightning rods out onto the plains during a thunderstorm. A lightning bolt came down, striking each rod in turn except the one held by Tala-El. Tala-El declared that a culture based on governmental science represented Krypton's best interests. As agreed, the delegates committed themselves towards forging Krypton's capital city as a technocracy.
Sin-Dar continued to serve as a councilor and statesman on the first Kryptonian Science Council – a position he maintained for the remainder of his life.
- This version of Sin-Dar (Earth-One), including all history and corresponding appearances, was erased from existence following the collapse of the original Multiverse in the 1985–86 Crisis on Infinite Earths limited series. Even though versions of the character may have since appeared, this information does not apply to those versions.
- Sin-Dar's final fate has never been revealed, but it is reasonable to assume that he passed away of natural causes long before the ultimate destruction of Krypton.
- 1 Appearances of Sin-Dar (Earth-One)
- 1 Images featuring Sin-Dar (Earth-One)
- Quotations by or about Sin-Dar (Earth-One)
- Character Gallery: Sin-Dar (Earth-One)