The Luck Lords are an alien race hailing from the gambling planet Ventura. Though originally seen in the 31st Century of the Legion of Superheroes, they have also been encountered in the 21st Century.
In the 21st Century, the Luck Lords take advantage of Destiny casting aside his Book of Destiny after encountering the Challengers of the Unknown, and through a complicated scheme involving an alien from the gambling planet Ventura, came into possession of the book.
The Book was then leaked to the Rannians, who were in the midst of the Rann-Thanagar War. With the book to counteract the Thanagarians Absorbascon, the war evolved into a thousand year long stalemate, with each side developing super advanced weapons that the Luck Lords used to further their conquest. When Batman arrived in the 31st Century, following a mishap with a Luck Lord weapon in a fight between the Fatal Five and La Dama, the Lords began draining the chronal energy from Batman to retroactively change history, eliminating all chance.
Through a complex plan involving Zeta Beaming through time to pick up Batman, Adam Strange, Hal Jordan, Supergirl and Batman are able to bring the Rannians and Luck Lords to the Challengers of the Unknown, where the Book of Destiny is unable to account for them. Adam Strange sends the Luck Lords into stable orbit around Oa, until the Guardians could arrest them.
In the 31st Century, where the Luck Lords were first seen, the Lords are used as fairy tales to frighten children. Criminals on the planet Thaun impersonated the Lords in an attempt to fight against the Legion. Despite their disguises, the Legion and the Legion of Super Pets were able to defeat the crooks, and the proper Lords arranged for the criminals to encounter an accident on their way to Takron-Galtos.
The Lords proper had planned to use Lightning Lad as a specifically foretold sacrifice during a "convergence of stars" to lead the universe into a state of "blissful" chaos. They attempted to sacrifice him three times, but failed each time. Since they ran out of time for the convergence, their chances to sacrifice Lightning Lad are moot.
Emerald Eye of Ekron
In a letter column of Legion, reader Andrew Capraro pondered if the Luck Lords had perhaps a connection to the Emerald Empress' Emerald Eye of Ekron. Paul Levitz remarked it was "an interesting suggestion." To date, no definite link has been defined, and current canon specifically contradicts it. Nevertheless, it is a fun footnote.