History
After discovering that the villain Metallo was powered by a heart made of Kryptonite, Lex Luthor used a sample to fashion a Kryptonite ring for himself. He wore the ring at all times in an effort to keep Superman away from him. Continued exposure to the low level Kryptonite radiation proved harmful however and Luthor developed cancer. To keep the cancer from spreading, his right hand was amputated and replaced with a cybernetic prosthetic (hidden under a black leather glove). At the time however the cancer had already metastasized and by then it was already too late. When Lex Luthor cloned himself a new body and returned to public life as Lex Luthor II, the cybernetic appendage was no longer necessary.
The ring eventually came into the possession of the Batman.[1] Although Batman is Superman's closest ally, he keeps the ring secured in the Batcave in case Superman ever loses control of his powers or if he falls under the control of an evil influence (such as Eclipso). On several occasions, Batman has been required to use the ring to keep Superman at bay.
Notes
- Superman has been known to carry a Kryptonite Ring in his belt buckle for when he fights other Kryptonians, an example of this is when he used the ring on Supergirl while she was under Darkseid's control.