First seen on TV's Smallville, the only time it was ever used on Clark was in the Season Four episode "Crusade", when he was reprogrammed as Kal-El. Martha Kent placed a chunk of Black Kryptonite (given to her by Dr. Swann's assistant, Bridgette Crosby) on his chest an
First seen on TV's Smallville, the only time it was ever used on Clark was in the Season Four episode "Crusade", when he was reprogrammed as Kal-El. Martha Kent placed a chunk of Black Kryptonite (given to her by Dr. Swann's assistant, Bridgette Crosby) on his chest and the two personalities physically split. Clark then used the Black Kryptonite to eliminate Kal-El. In the Season Eight episode "Doomsday" Chloe used Black Kryptonite to split Doomsday from Davis Bloome turning them into two different entities. During certain circumstances, perhaps only at the time of creation, Black Kryptonite can also affect humans, causing them to split into two different beings, one manifesting a good and pure personality, and the other an evil personality. The only case of it ever affecting humans occurred in the episode "Onyx" when an experiment with Green Kryptonite went awry and caused Lex Luthor to split in two.
In Post-Crisis continuity, Black Kryptonite was used by Lex Luthor at the behest of Darkseid to expose Supergirl's true "nature". It had one of two effects, on Kara Zor-El it split her negative persona from her pure self as it does in Smallville. While in Kal-El's case he said it stripped him of his sanity, turning him evil for an undisclosed time. In All-Star Superman Black-K has the effect of inverting the moral standard of the individual Kryptonian affected by it, turning Superman bad for a short time while also causing his abilities to weaken gradually alongside his mental acuity.
In Prime Earth continuity, The Batman Who Laughs used a modified version of it on his universe's Clark and Jon Kent to drive them into a killing frenzy, ripping apart their universe's Lois Lane and each other. He had previously used it on Supergirl, who tore her family to pieces before killing her.
In Justice League Action, it has similar persona separating effects, splitting Superman's good and evil sides, which wear a white and a black suit respectively.
On the TV series, Supergirl, the Black Kryptonite, also known as Harun-El, is a mineral with a mutagenic effect and seemingly magical powers, originating from the planet Krypton. It can be used as a source of energy. The black k's effects are similar in scope to that from hit TV Series Smallville, in its effect of splitting and recombining a Kryptonians divided selves. While a unique eugenics property it has is the bestowal of superpowers to both halved Kryptonians and Non-Kryptonian races.
In a complex long-running plot by Lex Luthor, he would galvanize Lena's use of the Harun-El as a medical procedure which acted both as an omni-cure all. As well as grant superhuman physical abilities on par with a Kryptonian or Daxamite. Abilities given through the substance are faulty however, prolonged withholding of Black Kryptonite in the system has debilitating to outright fatal side effects. Lex found a means of retaining his abilities without such drawbacks, anyone else using it require annual injections of Harun-El to stabilize their enhanced physiology.
The origins of this Kryptonite was most likely inspired by the Synthetic Kryptonite found in Superman III. In this movie, Gus Gorman attempts to create Kryptonite substituting an unknown ingredient with tar. While this version is still green in color it has the same effect on Superman as Black Kryptonite and as the main ingredient which differentiates it from normal Kryptonite is tar this most likely inspired the color of this type of kryptonite in other media.