Harun-El, also known as the Rock of Yuda Kal and referred to as Black Kryptonite by Lena Luthor, 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, healing, and power imbuement.
Harun-El was used on Krypton by the Children of Juru to imbue the Worldkillers with the dark magic of Yuda Kal. On their homeworld or in Argo City, it 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 (evil) and Samantha Arias (good). 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 the other half to Kaznia 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 who figured out how to make it.
Black Kryptonite also serves as a miracle cure for any and every conceivable form of ailment/disease imaginable, as was proven true by Lena's thorough experimentation. But it also has the side effect of giving potentially fatalistic superhuman abilities onto the host recipient, powers which put an enormous amount of stress on an organism's major metabolic functions; including cardiac malfeasance, blurred vision, debilitating migraines, neurocognative paralysis, and nosebleeds, among other possible complications.
As seen in the case of Ben Lockwood, these negative side effects can be negated by repetitious injections of Harun-El (though he only had access to an unfinished version of the serum), if only temporarily, as such a process briefly stabilizes the user. As seen with James Olsen, after the serum in his system became unstable, a second dose of the complete drug stabilized him. Lex Luthor, and Bitsie and Eve Teschmacher are the only ones who haven't been known to suffer any aftereffects.
- Dark Magic: The Harun-El is able to use dark magic that enables users to do a variety of things. One such is giving ordinary humans powers that allow them to go toe-to-toe with solar-powered Kryptonians or imbue the Worldkillers with the dark magic of Yuda Kal. Another use of Harun-El is that it is capable of allowing Worldkillers or Kryptonians to go to a place called the Dark Valley through their minds. In addition if Harun-El was exposed to solar energy. Then it has the capability to split a Kryptonian in two.
- Physical/Power augmentation: The Harun-El can be used to synthesize a chemical compound that would bestow a human being with extraordinary abilities. These abilities allow it user to go on par with solar powered Kryptonians, granting them the same set of powers a Kryptonian would gain under a yellow sun. Alternately, when mixed with other alien DNA, it bestows other alien abilities to humans, as shown with Eve Teschmacher (who was injected with Harun-El mixed with Kopy's DNA; granting Eve the ability to create clones of herself).
- Strength augmentation: The Harun-El seems to enhance the user's strength to the point where a human can physically combat solar-powered Kryptonians.
- Regenerative healing: The Harun-El bestows its user with a regenerative healing factor. Upon being injected with Lena Luthor's Harun-El drug, Lex Luthor and Bitsie Teschmacher were healed from cancer while James Olsen recovered from lethal wounds. When Lex used his Harun-El-empowered blood to give Red Daughter a blood transfusion, it managed to strengthen her weakened immune system and stabilize her physiology.
- Sensory augmentation: Due to being injected with the Harun-El, James can "zoom in" on people or things at a distance and even hear better than a normal human.
- Flight/Levitation: A few individuals who took the Harun-El serum gained unsupported levitation.
- Speed augmentation: Harun-El vastly bolsters personal locomotion by incredible strides; Ben Lockwood used his rapid motion to dispatch a platoon of Eve Teschmacher's clones.
- Durability augmentation: Physical resilience is likewise bolstered by Harun-El, enabling the user to be impervious to fire and hard impact.
- Heat vision: The visual receptors of the individual host of Harun-El allow for the accumulation and redistribution of ambient infrared, microwave or X-radiation as focused thermal blasts from the eyes.
- Harun-El Extractor/Anti-Serum: Lena created a serum that can extract the Harun-El from a user's system.
- Harun-El serum side-effects: The serum give superhuman abilities to the host, but it also puts an enormous amount of stress on an organism's major metabolic functions causing the users to experiment with time; i.e. cardiac malfeasance, blurred vision, debilitating migraines, neurocognitive paralysis, nosebleed, etc. The user's system can be stabilized temporarily by repetitious injections of Harun-El or by using the extraction serum.
Behind the scenes
- The concept of Kryptonite that grants humans superhuman powers was previously featured in Smallville, where various Kryptonite-afflicted meta-humans were the near-exclusive antagonists of the early seasons. However, in Smallville, the mutations were caused by Green Kryptonite.
- Black Kryptonite was also initially introduced on Smallville; first as a substance that was able to split both Clark Kent and Lex Luthor. They were split into two separate entities of themselves, similar to how it works in the Supergirl series as well.
- In the comics, Platinum kryptonite is a type of kryptonite that can permanently give humans Kryptonian powers.
- In the comics, humans can also temporarily gain the powers of a yellow sun-powered Kryptonian when affected by Superman vision. This is an additional power Kryptonians gain when exposed to a blue sun, while also having access to all the powers they'd usually have under a yellow sun.
- Humans and other non-Kryptonian species (such as cats) can also temporarily gain Kryptonian powers from exposure to X-Kryptonite, though this only lasts for 24 hours.