Each Green Lantern possesses a "power ring" that gives the user great control over the physical world as long as the wielder has sufficient willpower. While the ring of the Golden Age Green Lantern (Alan Scott) was magically powered, the rings worn by all subsequent Lanterns were the creations of the Guardians of the Universe, who granted such rings to worthy candidates. These individuals made up the intergalactic police force known as the Green Lantern Corps.

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http://en.wikipedia.org/wiki/Green_Lantern

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