Harun-El

The Harun-El, also known as the Rock of Yuda Kal, is a stone with magical powers, originating from the planet Krypton.

History
The Harun-El or the Rock of Yuda Kal, was used on Krypton by the Children of Juru to make the Worldkillers. On their home world or in Argo City, the Harun-El is harmless to Kryptonians but on Earth, the substance becomes toxic to Kryptonians and can be used to split a Kryptonian in two, such as when Lena used it to split Reign and Sam, into their good and bad side. When Kara used it to send herself, Reign and Sam into the Dark Valley to defeat Reign without casualties, it split Kara in two sending a demonic persona to Russia unbeknownst to her. Harun-El is also an incredible power source able to power the dome of Argo City as well as sustain an ecosystem and the artificial gravity on the asteroid that houses Argo. Argonians now have a recipe to make the substance from elements on Argo, courtesy of Lena Luthor who figured out how to make it.

Season 4
Harun-El