Green Lantern is the name of several superheroes, members of an intergalactic police force known as the Green Lantern Corps. They wield a power ring, one of the most powerful weapons ever devised.
A Lantern's power ring is capable of creating solid 'hard light' constructs from the wearer's imagination, which can be used to attack or defend. The greater the user's willpower, the more effective the ring. The upper limits of the power ring's abilities remain undefined, though it has been referred to as "the most powerful weapon in the universe" on more than one occasion.
The ring affords the wearer the power of flight and travel through space. It allows phasing through solid objects, invisibility, shape-shifting (through holographic disguises), accelerated healing of wounds, mental powers (telepathy, hypnosis etc.) and protection from biological threats.
Power rings are also semi-sentient computers through their connection with the Book of Oa - they can be used as a database, translator and communicator (between ring-bearers).< LESS