The Green Lantern

A well established and much loved character, The Green Lantern's mythology spans thousands of years and thousands of storylines!
Each Green Lantern is in possession of a power ring, which gives its user control over the physical world.
Alan Scott, considered to be the Golden Age Green Lantern, was a young railway engineer who stumbled upon a magically powered lantern, from which the green flame instructed him to craft a ring.
The rings worn by subsequent Lanterns were technological creations of the Guardians of the Universe, who granted them to worthy candidates.
After Alan Scott came Hal Jordan, considered the Silver Age Green Lantern.
Jordan was a test pilot who is given the ring by the dying alien Abin Sur, who tells Jordan that he used the ring to seek out someone who was "utterly honest and born without fear" to take his place as Green Lantern. Jordan went on to become a founding member of the Justice League of America.
Moving into the Bronze Age of the Green Lantern and Guy Gardner is also in possession of the ring.
Abin Sur originally chose Gardner to pass the ring to, but when his ship crashed and he was mortally wounded, Hal Jordan was closer.
Gardner therefore became a 'back up' Green Lantern, stepping in to replace or assist Hal Jordan when needed.
But tragedy strikes early in Gardner's career when a power cell explodes and puts him in a coma.
He is replaced by John Stewart, an out of work architect, who is selected by the Guardians to act as a back up to Hal Jordan.
In the Modern Age, Kyle Rayner is chosen by the last Guardian of the Universe to become a new Green Lantern with the last power ring.
A struggling freelance artist, Rayner is quite unlike any Lantern who has come before him and it is revealed that he was selected because he knew fear.
This allowed Rayner to go on and defeat the omnipotent being Parallax.