Zundernell, the Golden Lantern, was the custodian of the Cosmic Grail hidden in the destroyed earth 15. The time he was working there is unknown but it is probable to be measured in thousand, even millions of years. The loneliness of his task broke the spirit of Zundernell and he emited a signal asking for help, fearing the coming of an inminent crisis on the multiverse. Green Lanterns from several parallel universes answered his call but the diference of size was felt like an insult for Zundernell who trapped the Lanterns, to use them as warriors for his uncoming menace.
After being freed by Hal Jordan of earth 0 and Carol Ferris of earth 11, the lanterns subdued Zundernell and put him under prision, believing him to be desilusional, with the Cosmic Grail being only an damaged power battery and the crisis, a figment of his insane imagination.
Yet, it it possible than Zundernell is right about both, the Cosmic Grail and the uncoming crisis, unfortunately for the multiverse.
The Golden Lantern was created by Grant Morrison and Liam Sharp. His concept is inspired in the figure of Don Quixote de la Mancha.