In the beginning...
About 10 billion years ago, Krona existed as a member of a race of immortals. At some point in his history here, Krona created a map leading to a great source of power. This map was stolen from the Guardians' vaults and the thieves would follow its instructions to find the Orange Light of Avarice. During this period, Krona protested his fellow Maltusians contempt for emotions; they had chosen to become emotionless in preparation for their roles as the Guardians of the Universe. Krona created a prototype gauntlet that used the Green Light of Willpower. This technology would later be used to create the Green Lantern Power Rings. During this period or shortly after, Krona was also in charge of keeping the Emotional Embodiments imprisoned, furthering his knowledge of the various emotional powers.
Later, Krona was attacked by the Manhunters, the emotionless, robotic police created by the Guardians. He managed to destroy one using his gauntlet, and reprogrammed one. The Manhunters were reprogrammed to annihilate all life in Space Sector 666; specifically, the planet Ryut, home of Atrocitus, who was one of the five survivors, later known as the Five Inversions. When approached about why he had done this, Krona claimed it was to show the flaws of an emotionless police force. This lead directly to the Guardians abandoning the Manhunters and forming the Green Lantern Corps. During his escape, he inadvertantly coined portions of the Green Lantern Oath; specifically, "Beware my power/ Green Lantern's light."
At a later point, Krona devised a machine with which he planned to see back through time to the beginning of all things. Krona was acting in defiance of an ancient legend that warned that if anyone ever discovered the true origins of the cosmos, both the they and the universe would be destroyed. Despite pleas and urges by fellow Maltusians to desist in his endeavors, Krona worked until his invention revealed the image of a shadow shaped like a giant hand holding a galaxy at the Dawn of Time, this hand is implied to belong to Eternity. At that instant, a bolt of cosmic lightning destroyed the machine, and would have killed Krona had he not been virtually indestructible.
Krona's act had several repercussions. It caused the birth of evil itself throughout the universe causing hatred and violence. It also triggered the creation of the extra-dimensional Antimatter Universe. It also caused Krona's own universe to replicate itself an unknown number of times. Thus the single universe became a multiverse, a collection of parallel universes. Only eons later would the multiverse be reduced to a single universe in the Crisis on Infinite Earths, and the true consequences would be revealed then: this reckless experiment aged the Universe and shortened its lifespan by more than a billion years. It also became apparent the giant hand Krona had witnessed was, in fact, that of the Anti-Monitor.
The Maltusians punished Krona by reducing his form to disembodied energy doomed to travel harmlessly through the multiverse forever. Then, to atone for Krona's crime, the Maltusians vowed to create a force for good. Eventually, they became the Oans known as the Guardians of the Universe, creators of the Manhunters and, later, founders of the Green Lantern Corps. In recent years, Krona used the mystic energy of the Starheart belonging to Alan Scott, Earth's Golden Age Green Lantern, to make possible his return to his original form. Krona again attempted to probe the origin of the universe, but was halted by Scott and Hal Jordan. The Guardians again reduced Krona to energy form and exiled him to the void.
Eventually Krona entered the dimension ruled by Nekron, where all the souls of the dead pass on their way to their final destination. His arrival there was foreseen by a giant tear in the wall separating the dimensions because of the impossibility of an immortal in the land of the dead, and Nekron wished he could pass through the gate, but it was too small. Nekron restored Krona to his original form and greatly increased his strength and powers. He then sent Krona on a mission to destroy the Guardians and the Green Lantern Corps to widen the rift so he could pass through to the Universe. Although he was able to kill a few Guardians and some Green Lanterns, thus making the rift between Nekron's realm and the realm of the living to increase in size, he was eventually defeated once more by the rest of the Green Lantern Corps and was sealed into Nekron's realm by the remaining Guardians.
Traversing the Multiverse
Krona, undeterred, was shunted into other universes. These lacked the sheer power necessary to deal with the malevolent entity's dreams and desires, and in his quest to watch the origin of an universe, he destroyed countless of them in his path, including the Telemachus Universe. In his celestial wandering, Krona came across the Marvel Universe, Earth-616, and found an entity capable of fighting one of his probes, the Grandmaster. He threatened to destroy that universe as he had done to countless others, but the Grandmaster tempted him with the knowledge of an entity which resided in his universe capable of offering Krona the answers he wanted, for it had seen the death and rebirth of an universe and lived.
Krona demanded answers, but the Grandmaster challenged him to a game to stall him, knowing full well Krona would not abide by the rules if he lost. The Grandmaster would give Krona the knowledge he needed if he lost, but Krona would leave Earth-616 if he was on the losing end of the bargain. The game consisted of the two premier superhero teams of each universe, the JLA and the Avengers, rallying to retrieve twelve artifacts of colossal might scattered through both universes. The JLA would represent the Grandmaster, and the Avengers would fight on Krona's side. Logically, neither of the teams was informed of the full situation and was tricked into conflict with its counterpart.
Krona, as foreseen, was impatient and wished for the game to end swiftly; though the end resulted in a victory for the JLA, granting the Grandmaster his winnings, Krona refused to allow this and drained the knowledge from his mind, forcibly summoned Galactus, and engaged him in a battle for the two universes. Krona won, and though he was swept up in a trap engineered by the Grandmaster, he instead ended up using the trap to fuel his efforts, using the remains of Galactus to create a citadel to force the collapse of both universes to watch the birth of a new one with the twelve artifacts.
The first blow came when Hal Jordan, restored as Green Lantern by the multiverse, together with the Avengers' Scarlet Witch, managed to block his attempts at directly merging the Earths and set him back. Then, the two teams grouped together to stage an assault on Galactus' remains and defeat Krona. In response, Krona started ripping military forces from both Earths and brainwashed them to force subservience to him. These forces included terrorist organizations, supervillains, and rogue military cells. Nevertheless, as soon as he could, the universes started sending over countless heroes as well, and Krona ended up losing when a divinely-empowered Superman destroyed the walls of his final keep and Flash, acting as a distraction, allowed Hawkeye a direct demolition shot at Krona's machinery. The blast was immense, and ended up sucking Krona into the universe seed called the Cosmic Egg.
Within the Egg, he became the Firstgod, a being of unimaginable power, and with the first living, sentient beings under his command, he ordered them to search forever for knowledge, mirroring his own attitude. For eons within the Egg, years outside of it, Krona brutalized his subjects in his quest for knowledge, augmenting his power, and escaping at the first offered chance, when the Dark Trinity used the Egg to usurp the power of Superman, Batman, and Wonder Woman. He first approaches the Controllers for help in contacting the consciousness of the universe, and is promptly betrayed by them. Destroying their laboratory planet, he hears a whisper of thanks from the dying planet, which had been lush with life and vegetation before the Controllers wiped it all out for their laboratories. This leads him to suspect all planets have consciousness themselves, and approaches Earth, knowing of its place in the cosmos.
Leaving, he seeks an old weapon of the Qwardians, which he had a hand in creating: the utterly unrelenting Void Hound. Upon finding the super-weapon, now a living form of Oan and Qwardian technologies, he saw it had become a true living being, and offered it a chance to hunt for him. Surprised he had been given choice, the Hound agreed to fight for Krona. Later, when watching above Earth the events of Trinity unfold, the Dark Trinity arrived. Morgaine Le Fey offered him to imprison the Worldsoul, the Earth's living soul, in exchange for aid against the coalition formed against the Dark Trinity, but asks for a replacement. Krona indeed offers to give them support, and to place the innocent soul of Stephanie Nashton in the Worldsoul's stead. Enigma protests against this, but is ultimately overruled and sent back to the Antimatter Universe.
Krona, however powerful, was entangled in the magic Morgaine had woven to exile the Trinity, and with Sun-Chained-in-Ink, the Void Hound, who had been drafted into the service of the Nightlord (Batman's divine form), and the mystic Tarot, would have been thrust into the universe of the Egg if Morgaine had not lent him her powers, allowing him to break through and destroy Earth. Confronting the Worldsoul, he demands answers to his questions, but is left nothing short of horrified when he realizes the Worldsoul's answers, which state she has no true purpose other than to exist and coexist with the Universe at large in a Great Dance, making Krona's entire quest essentially meaningless. Krona attempts to seize her and force answers out of her, but he is stopped by the Divine Trinity and shunted into the Egg's dimension again, powerless. There, he is confronted by a Sunlord, a Truthlord, and a Nightlord, who strip him of his latent power, and to sate his curiosity about what it entails to be the consciousness of a universe, he is forced to experience the birth of the reality within the Egg as Earth-1 and being imprisoned himself to serve as its Worldsoul.
Recently, Krona has returned to the mainstream DC universe in the wake of Nekron's defeat during Blackest Night and has been collecting all of the Emotional Entities for an unknown purpose. The first act of Krona's plan occurs with his abduction of the fear entity Parallax during the finale of Blackest Night, imprisoning the creature within the confines of an ancient temple marked with the symbols of the Emotional Spectrum. It is revealed that he has used Maltusian Evolutionary Bandages to hyper evolve into a Guardian of the Universe state, rather than his original, Maltusian form, or his energy form.
Krona then proceeds to remove Ion from Sodam Yat, effectively turning Daxam's sun from yellow back to red and killing hundreds of Daxamites in the process. Over the course of the story arc, Krona is shown working with Hank Henshaw, telling him that enslaving and altering the qualities of the Alpha Lanterns will restore his mortality and also lead to the destruction of the Green Lantern Corps. In addition, he is shown working with the telepathic Zardor in his plot to brainwash rookie members of the Green Lantern Corps for his own purposes.
Krona later appears on the Eastern Seaboard of the United States -- with an obedient Parallax in tow -- to Hal Jordan, Nicole Morrison, Larfleeze, Saint Walker and the Indigo Tribe, seeking to obtain both Adara and Proselyte for his entity collection. When confronting Jordan and the others, Krona reveals that, prior to his banishment by the Guardians, he was the caretaker responsible for protecting the entities, and that is why he can control them and the abilities they possess. When Sinestro and Atrocitus join the battle, Krona is able to take the Butcher for his collection as well before taking off to Zamaron, still recovering from the attack of Queen Shrike and the Manhawks, and collecting the Predator, which finishes his collection.
Seeking his control over the various corps, Krona returned to Oa and instilled each of the entities except for Parallax into each of the Guardians of the Universe taking control over them. He then placed Parallax back inside the Central Power Battery and in doing so, reinstalled the impurity throughout the Green Lantern Corps leaving them to go to war with their fellow corpsmen over their fears for each other. The impurity causes any Green Lantern connected to the Central Power Battery to lose their free will and become slaves to Krona. The possessed Mogo begins sending out thousands of Green Lantern rings to unworthy beings, resulting in a massive Green Lantern army of mindless, violent slaves.
Krona later captures Hal and Guy and chains them. He plans to hyper evolve them using the evolutionary bandages. When John Stewart kills Mogo using the power of the Black Lanterns, channeled through the Indigo Ring he is wearing to keep his free will, Hal and Guy are able to escape. The four Earth Green Lanterns are able to free Parallax from the Central Power Battery, freeing the Corps from Krona's control.
Blood and Rage
After his death, Atrocitus takes Krona's lifeless body to Ysmault, where he confides in the dead Guardian that he is like a jealous lover that Hal Jordan got to kill the Guardian instead of him. Later, Krona body is stolen by Abysmus, and eaten, so that Abysmus could gain Krona's power.
Green Lantern (2011)
Krona appears in the live-action film as a former Guardian who intended to prove his fellow Guardians wrong about the yellow power of fear to be uncontrollable, but when he tried to control and use its powers for good he instead becomes a host for Parallax, who feeds upon the fears of others and wipes out entire races and sectors. He was eventually defeated by the Green Lantern Abin Sur in the Lost Sector and was encased in a emerald green crystal, to be trapped there for eternity. When three alien astronauts arrived, it enabled him to use their fear to return to his former glory and escape from his prison to exact revenge upon his jailer, Abin Sur. Yet again he is defeated by the same power ring but this time worn by Hal Jordan using the gravitational pull of the Sun to burn Parallax.
Green Lantern: Emerald Knights
Krona will appear in the direct-to-DVD animated film as the primary antagonist. In the trailer, he is shown to resemble his Firstgod incarnation from "Trinity" rather than his more traditional Maltusian appearance.