Once a Guardian of the Universe, Ganthet was exiled from Oa along with Sayd, a fellow Oa'n. They went on to found the Blue Lantern Corps, the heralds of Hope. Ganthet inducted himself into the Green Lantern Corps to aid in the fight for the Blackest Night.
One of the founding members of the Guardians of the Universe, creators of the Green Lantern Corps, Ganthet has played a large roll in the history of the Corps.
Ganthet is the oldest living Guardian of the Universe, and last of the Maltusians that voyaged to Oa from Maltus. Already considered by many, the most powerful of the Guardians, it came as no surprise that he alone survived Parallax's attack. though the effect of their rebirth at Kyle Rayner's hands have had an unknown affect on his power. Displaying an uncharacteristic interest in the affairs of humans Ganthet, served alongside Zeus, Shazam, and the Highfather in the Quintessence to keep watch over the Earth. Ganthet also had the distinction of being one of the few Guardians with which the Corps members felt they could Identify with. Despite these differences Ganthet began life much the same as any other Guardian...
Maltus, home planet of the Maltusians, a race so old, theirs was the apex of civilization when the first signs of life began appearing across planets of the universe. The blue skinned humanoids of Maltus were the immortal beings responsible for creating the scientific utopia that defined their planet. Eons of evolution and scientific discovery had gifted the Maltusian people with powerful telepathic and cosmic powers. The paradise the Guardians created seemed as though it would last forever, until the greedy ambitions of their finest scientist lead to its utter ruin. The Maltusian Krona, obsessed with gaining knowledge at any cost, had created a time machine against the wishes and warnings of his fellow Maltusians. Krona used his machine to gain the knowledge of creation itself, traveling back in time to witness the Big Bang.
In his hubris, Krona unleashed an explosion of Anti-matter, erasing billions of years from the time-stream. The backlash of the devastation wrought by the explosion unleashed a new threat unto the cosmos. For the first time, evil had awakened in the Universe.
The vast amount of Anti-matter released in the explosion coalesced itself into the Anti-Matter Universe, and from the shattered fragments of space and time, the Multiverse was born. More seriously, the Maltusians knew that, as it had in the past, the universe would one day contract upon itself to be reborn by a new "big bang". Due to the anti-matter unleashed by Krona, the universe was deprived of sufficient matter necessary to ignite a new "big bang". As a result of Krona's actions, the universe and all existence would one day simply die out, never to be reborn.
Feeling responsible for this, the Maltusians relocated to the planet Oa, located at "the center of the Universe", and became the Guardians of the Universe. Their goal was simple: combat evil and create an orderly universe. And they acted quickly on that goal. During this transitory period, the Maltusians' appearance changed as they adapted to their new life as Oans.
When a renegade Guardian Dawlakispokpok (Dawly) attempts to use a time machine to change history Ganthet must call upon the greatest Green Lantern,
Hal Jordan, for help. Dawly, planning to use his own time machine to send Krona to the end of time,and prevent him from creating the Anti-Matter Universe, Hal and Ganthet arrive to stop him . In the ensuing battle Hal discovers that it is in fact Dawly that was responsible for the universe being "born old". After his defeat, Dawly and his family are brought before the Guardians to stand trail, during which the Guardians erase the memories of all those involved. Ganthet however decided to shield Hal's mind, allowing him to retain his knowledge of on of the Guardians' darkest secrets
After losing their greatest Lantern (Hal Jordan) to insanity, and the destruction of the Central Power Battery, the Guardians decide transfer all of their power to Ganthet, leaving him as the last remaining Guardian. Creating one last Green Power Ring from the remains of Hal Jordan's ring, Ganthet goes to Earth to find a new Green Lantern. After being turned down by his first choice Guy Gardner, Ganthet settles for Kyle Rayner, a struggling artist, reluctantly bestowing him with the ring, saying "You shall have to do".
Kyle. During Kyle's first few months as a Green Lantern, Ganthet is rather unimpressed with him and decides to take back his ring. Kyle is finally able to prove his worth by facing Parallax without his Power Ring.
Ion and Restoration of the Corps
After absorbing the residual energy of the sun after the Final Night, Kyle Rayner became the godlike Ion, a being even more powerful than Parallax. Soon coming to realize that continuing to wield Ion's power would cost him his very humanity, Kyle travels Oa and uses his power to recharge the Central Power Battery and restore the Green Lantern Corps. With the Central Battery restored, the a new group of childlike Guardians are born, both male and female. Entrusting Ganthet to raise and care for the new Guardians, teaching them to use their great power, and to embrace emotion rather than purge themselves of it. One Guardian in particular, a small girl named Lianna, demonstrated a proficiency and aptitude for her powers that far exceeded that of her peers. When a peaceful world under the Green Lantern's jurisdiction comes under attack, Ganthet realizes that Lianna has disappeared and so sends Kyle and Jade to investigate while he searches her. Upon their arrival Kyle and Jade come under attack from a female warrior, the missing Lianna. Arriving on scene, Ganthet qualms the fighting and take Lianna back to Oa, apologizing for his arrogance in thinking he could care for all the new Guardians himself. Deciding to seek aid in order to prevent such an event from occurring again, Ganthet sends for the Zamarons to aid him in raising the new Guardians.
Seeking knowledge of Parallax, Kyle Rayner travels to the end of the Universe. Upon his return Kyle relays his findings to Ganthet. Concluding that Parallax must have altered his memory after their last encounter, Ganthet tells Kyle the whole story behind the birth and imprisonment of Parallax. Realizing that their only hope my lay with Hal Jordan, Ganthet instructs Kyle to retrieve Jordan's corpse, so as to bring about his resurrection. Leaving immediately, Kyle is attacked by Kilowog, a fellow Green Lantern. Under Parallax's control Kilowog tried to kill Kyle, but is stopped by Ganthet. Releasing Kilowog, Guy Gardner, and John Stewart, Ganthet sends Kyle on his way. Discovering that Hal's corpse still holds remnants of Parallax, it takes the combined efforts of Hal and the Spectre to fully cleanse his soul. Purged from Jordan's body Parallax instead, bonds itself to Ganthet. Just before he is taken, Ganthet sends a beacon of energy to guide Hal Jordan's soul back to his body. Now fully purified and resurrected, Hal Jordan leads the Kyle Rayner and the other Lanterns in defeating the Parallax-possessed Ganthet, returning Parallax to its prison in Central Power Battery.
In the aftermath of these events, all of the new Guardians are restored to adulthood, becoming as cold and manipulative as their predecessors. The only notable difference being addition of female Guardians to their ranks. Ganthet, as ever, maintains his belief that they should embrace their emotions.
Sinestro Corps War
As events are set in motion that will ignite the long awaited war between the Green Lantern Corps and the Sinestro Corps, Ganthet and fellow Guardian Sayd are their order for embracing emotion.
Having finally regained its true, monstrous form, Parallax attacks the Earth Lanterns for freeing Kyle Rayner from his control. Ganthet and Sayd arrive just in time to save them by banishing Parallax into their four power batteries (Hal Jordan's, Kyle Rayner's, John Stewart's, and Guy Gardner's, respectively). After revealing his and Sayd's expulsion from the order, Ganthet uses the last of his Guardian power to forge a new power ring for Kyle, and asks that he step down as Ion, to which Kyle readily agrees. Taking up their power batteries, the four Earth Lanterns hear the Sinestro Corps oath echoing in the distance, and, as one, recite the Green Lantern Oath, and depart to confront the Sinestro Corps.
To prepare them for the battle ahead, Ganthet and Sayd reveal the emotional energy spectrum created at the start of the universe. The seven colors of the emotional spectrum: green (will), yellow (fear), violet (love), red (rage), indigo (compassion), orange (greed), and blue (hope) each derive their power from their respective emotions. Those colors closest to either end of the spectrum are far more dangerous and unwieldy, often corrupting those they empower after prolonged use. Ganthet also reveals that, in the very near future, each color will develop its own Lantern Corps of followers, all gathering to fight one another, culminating in a War of Light that will lead to the cataclysm t known as the Blackest Night, the darkest secret concealed within the Book of Oa.