Ganthet is one of the Guardians of the Universe. Unlike his peers, Ganthet shows more emotion and has his hair unkept. When presented with the mystery of Green Lantern deaths in Frontier Space, Ganthet chose to show off an experimental space ship to Hal Jordan and Kilowog. Knowing full well the other Guardians would never sanction a resuce mission, Ganthet's move paid off and the duo took off with the ship. They were unaware Ganthet had placed a prototype power battery aboard the ship. When Jordan and Kilowog spoke with Ganthet and Sayd about trying to use diplomacy and revealed the origins of the Red Lanterns, Ganthet revealed the connection between the Guardians, the Forgotten Zone, and the Manhunters. Ganthet spoke with Appa to activate the prototype and save Betrassus. Appa, however, realized Ganthet was clouded by his emotions and had him banished from Oa. Sayd came to trust Gathet and secretly reprogrammed his vessel to return to Oa once it was launched. Ganthet then activated the prototype battery and left Oa for good.
Ganthet journeyed to the planet Odym and helped start the Blue Lantern Corps. After some time and effort, he managed to get a Blue Lantern Central Power Battery fully operational after receiving a visit from Hal Jordan, Kilowog, and Aya. Jordan needed Ganthet's help in trying to find more defensive flaws in the Manhunters. However, that was sidelined when the Central Power Battery amplified the Manhunter aboard the Interceptor and three in space near the planet. To make matters worse, it would take Ganthet several hours to extinguish the battery's flame. Once the Manhunters were destroyed, Ganthet extinguished the flame and reminded Jordan that hope always remains regardless of the battery being online or not.