Sinestro is a former Green Lantern and mentor of Hal Jordan. Found guilty for crimes against his own planet, he was banished to the Anti-Matter Universe. There he acquired a power ring that harnessed fear as opposed to the Green Lantern Corps' willpower. With this new yellow colored ring and a vendetta against all Green Lanterns, he causes great havoc on Earth and existence as a whole. He is also the leader of the Yellow Lantern Corps.