Mogo was a sentient or "living" planet. When it was desired, its affliation with Green Lantern Corps was marked by its folliage that was arranged into a green band circling the body with the standard Corps lantern symbol. Mogo is also responsible for guiding the Green Lantern rings to new sentient beings after their hosts die.
Mogo was not a social Green Lantern (Roche limits being what they are) and its interactions with the rest of the universe were not well-documented. It avoided announcing its presence, preferring to represent itself using pseudonymous holograms. In one incident, it sent holograms to purchase Lobo's dolphins. When Lobo tried to retrieve them, a Mogo hologram persuaded him not to. Lobo never discovered he was dealing with a sentient planet. At the same time, Mogo has allowed alien races to live on its surface and has been willing to change its climatic conditions to suit them. These inhabitants of Mogo may not always know that their home is alive and watching them.
Mogo was also the adopted home of a group of Xenomorphs. It seems that years ago, Hal Jordan and a group of fellow Green Lanterns were charged with dealing with these Xenomorphs following the death of a Green Lantern, and Hal Jordan wanted to avoid killing them if possible, believing that they were just animals, and thus were not evil. His solution was to deposit them on Mogo, where they would be a threat to no one and would be able to live. Years after that, however, Kyle Rayner traveled to Mogo to rescue the crew of a crashed freighter. This was Rayner's first encounter with the sentient planet, although he didn't speak to Mogo directly.
Mogo traveled to Sector 1014 to seek the aid of Ch'p when he lost contact with the power battery on Oa. Mogo was unaware that the battery had been destroyed and that Ch'p had been killed. Having relied on the emerald energy of the power battery to sustain him, Mogo lost consciousness and drifted through space until he was discovered by a nomadic alien race. These aliens proceeded to strip Mogo of his natural resources and pollute his environment. Mogo's body reacted instinctively, creating constructs to hinder the aliens' efforts to exploit his resources. Mogo was finally rescued by Kyle Rayner, who used his power ring to reawaken the sleeping giant. Mogo offered to allow the aliens to settle on him and offered to take care of all their needs, but the stubborn beings chose to abandon their settlements. Mogo later revealed to Rayner that he was relieved the aliens had left, and that he had planned to give them terrible weather in retaliation for their pollution.
Following the resurrection of the Guardians of the Universe and the reestablishment of the Green Lantern Corps, Mogo rejoined the Corps. Mogo requested back-up against Rannian and Thanagarian forces. Green Lanterns Kyle Rayner, Guy Gardner, Stel and Green Man were dispatched to clear out the enemy fleets, and then enjoyed a respite on Mogo's surface. Mogo had also changed his policy on isolation, now encouraging Green Lanterns to come and enjoy rest on his surface. He has also given counsel to Green Lanterns struggling with their new dual lives. At one point Despotellis infected Mogo with mushroom spores, causing the Green Lanterns receiving counseling to be infected with hallucinations and then driven mad. Guy Gardner, despite being framed for murder caused by this event, managed to figure out what was happening and confirmed it when medic Soranik Natu conducted an analysis on Mogo. Guy and several other Green Lanterns succeeded in removing Mogo of the spore's influence, allowing Mogo to destroy the mother spore.
The Battle of Mogo
Mogo played a major role in the conclusion of the battle against Superboy-Prime, in which the Green Lantern Corps, Superman and Kal-L to stop the villainous Superboy-Prime. The Supermen, Kal-El and Kal-L, took the deluded Superboy-Prime into the red sun Rao in a desperate gamble to depower him. With their powers waning, the Kryptonians managed to crash land on Mogo, before they would all perish in deep space. The Supermen managed to stop Superboy, but not before he managed to critically injure Kal-L. After the fight, the rest of the Green Lantern Corps took Superboy-Prime into custody.
Sinestro Corps War
During the Sinestro Corps War, Mogo was responsible for directing Green Lantern Rings to potential new bearers after their Green Lanterns died. Because the Corps was in a constant state of recruitment, he was targeted by the Sinestro Corps for destruction. They used Ranx the Sentient City, enlarged to Mogo's size, to drill to Mogo's core, where the Children of the White Lobe would detonate blink-bombs and kill Mogo. Green Lanterns Kilowog and Salakk lead a force of Green Lanterns to defend Mogo. The Guardians, seeing the number of Green Lanterns dropping while the Sinestro Corps remained static, authorized the Lanterns to use lethal force against their enemies. Sodam Yat destroyed Ranx before he could kill Mogo, and the Sinestro Corps were deprived of their only viable method of attacking Mogo, who was now even more dangerous since he could kill. After the conclusion of the War, Kilowog enjoyed a brief leave with energy constructs of his deceased family on Mogo.
In a prophecy narrated to Abin Sur, it is said that Mogo will be the last Green Lantern. In a battle with the Empire of Tears, Ranx the Sentient City will explode a blink-bomb within Mogo's core, killing the sentient planet and ending the Green Lantern Corps forever. The events of the Sinestro Corps War seem to have disproved this prophecy.
Mogo plays a significant role during the Blackest Night. During the John Stewart (New Earth) Lantern attack on Oa, Salak orders that all the rings of deceased Lanterns were to head to Mogo, so that the new recruits would not be taken to Oa during the battle. Mogo itself traveled to Oa to help with the battle by increased his gravity to pull the Black Lanterns off of Oa, unfortunately he also drew his fellow Green Lanterns along with them. Once there Mogo pulled all of the Black Lanterns into his core, where their bodies were constantly being incinerated, preventing their regenerative powers from fully restoring them.
Mogo also helps to free Guy Gardner from the infulence of the Red Latnern power ring, however he is unable to completely erase its influence and warns Guy of this.
War of the Green Lanterns
Krona, the mad guardian, took over the Green Lantern Corps by implanting Parallax in the Central Power Battery. The takeover included Mogo, who Krona used to recruit more members of the Green
Lantern Corps. Kyle Rayner and John Stewart, wearing Blue and Indigo rings respectively, attempted to free him from Krona's control using Kyle's Blue Power Ring. They found Mogo's core, but were assailed by the controlled Corps. They found residue from the Black Lanterns that Mogo had absorbed in the Blackest Night. John was also telepathically connected to the corrupted Mogo, and Krona determined that he could not be freed. Channeling the Black energy with his Indigo Power Ring he produced a massive blast of power that killed Mogo. This produced a wave of psychic feedback that temporarily paralyzed Krona and the Corps.