Power ring

A power ring is a type of technology developed by the Oan civilzation of an. The power ring is a conduit for energy when worn by a person and attuned to energy fields of a battery.

The guardians of Oa crafted a green ring that was a focus of willpower and gave the ring to champions of the Green Lantern Corps, named for their glowing green power batteries. Eventually, other power spectrums were used, such as the Yellow Lanterns that take advantage of the yellow spectrum impurity in a Green Lantern's ring, or the Blue Lanterns who focus the power of hope over willpower.

fled to alternate reality (Nero, 2233)the reality where had defeated, and deposited an array of spectrum-powered rings. The Blue Lantern ring selected as its bearer and the yellow ring chose, a Klingon general.