Kryptonite (Smallville)
From Multiversal Omnipedia
Kryptonite is an element created from the substance of the planet Krypton after its destruction. A radioactive element, it weakens and eventually kills Kryptonians. It can also cause mutations in normal humans, giving them super-powers that often reflect their personalities or desires. Red Kryptonite also exists, which can negatively affect Kryptonians' minds.
