Legion is a supervillain from the DC Comics universe. He was created by Keith Giffen, Gerard Jones, and Romeo Tanghal. He is a foe of Abin Sur, the Green Lantern of Sector 2814, the Silver Age Green Lantern and the Green Lantern Corps. His only appearance is in the 1990 mini-series Green Lantern: Emerald Dawn.
Legion was introduced in the 1990 comic mini-series Green Lantern: Emerald Dawn, which covers the early days of Hal Jordan's career as the Silver Age Green Lantern. Jordan took the opportunity to go to Abin Sur's spaceship to recharge his ring, which again attracted Legion. Jordan detonated the ships reactors, using his ring to protect himself, and afterwards believed Legion to be dead.
However, Legion reached the Guardian's citadel, but Jordan shattered his armor, believing this would kill him. Instead, its consciousness absorbed the power of Oa and grew to immense proportions.
Legion has been retconned out of DC comics continuity following the events of Infinite Crisis and the Sinestro Corps War (as explained in the "Secret Origin" arc of Green Lantern [Vol. 4]).