Krona is a fictional character that appears in comic books published by DC Comics. The character first appeared in Green Lantern #40 (Oct. 1965), and was created by writer John Broome and artist Gil Kane.
Krona returns to a physical state using the energies of Alan Scott's mysical power ring, but is again turned into his energy form by the Guardians. Krona is finally restored to his original form thanks to Nekron and attempts to kill all of the Guardians.
Krona later resurfaces as the manifestation of Entropy itself and battles the New Guardians. While trying to discover the secret of universal creation, Krona is destroying entire universes and arrives in the Marvel Universe, where he agrees to a cosmic game with the Grandmaster; two teams, one from each universe, seeks out items of great power. Should Krona's team (the Avengers) win, Grandmaster will give the knowledge Krona seeks in return for not destroying his universe. But when Grandmaster's team (the Justice League) wins, Krona in fury strikes down the latter, and then continues his onslaught to destroy both the Marvel and DC universes in order to create a new one, so that he could watch creation first-hand. In the end, thanks to the joint actions of both teams, Krona is imprisoned into a "cosmic egg", from which a universe eventually will be born.
Like the rest of his species, Krona possesses enhanced physical abilities; vast psionic powers, telepathy and telekinesis; and virtual immortality; does not need to breathe, eat or sleep, and can regenerate health at an accelerated rate. His powers were later increased by Nekron, making him more powerful than any of the Guardians.
As Entropy, Krona was composed of anti-energy, could absorb others into his body, converting them into more anti-energy, and was able to create an army composed of anti-energy that were completely under his control. During the JLA/Avengers miniseries, where he wielded the power of all the universes he had previously destroyed, Krona proved able to easily defeat both the Grandmaster and Galactus.