Krona was a powerful being known as the Mad Guardian whose actions had an unintended consequence on the universe.
Once a member of the Guardians of the Universe, Krona expressed free will and was an independent thinker who believed that the Guardians required emotional beings to police the galaxy.
Desiring deeply to see the beginning of the universe, Krona began his mad experiment but continued on with it despite the warnings of Ganthet. Witnessing the Hand of Creation, Ganthet noted a power ring on it after which a cosmic bolt disrupted Krona's experiment. Splintering Krona's machine, it ended up having reverberations across the entire Multiverse. As the dust cleared, Krona discovered Volthoom and his space ship from Universe 3 to have arrived.
Krona's corpse was collected by Atrocitus, who kept it on a shrine in order to worship their "marriage in rage" and keep memory of his death at Jordan's hand. Atrocitus would often confide his empty and shallow thoughts with Krona's corpse. The corpse was Krona was in reality possessed by Abysmus who used the power in his body to create a race called the Abysmorphs.