The Lapis Lazuli was created when the Land of Dragons and the land of Pirra collided with one another. It was gifted to the Mere tribe and became their talisman. It was said to have a special connection to the Opal, the gem of the Plains tribe.
Sixteen years after it was added to the Hive, the Lapis Lazuli was recovered by Lief, Barda, and Jasmine. Lief pried it from the Hive's cone of treasure and replaced it with a wooden bird Jasmine won in Rithmere. He placed it in the fourth medallion on the Belt of Deltora and it gave the companions safe passage out of the Sands.
The Valley of the Lost
Lief touched the Lapis in order to repel the magic of the the Guardian. Still, the Guardian attacked Lief but he touched the Belt while doing so and this caused him to be attacked by his own creatures.
The Lapis Lazuli woke Fortuna from her slumber and gained more power once the dragon had been awakened.
Isle of the Dead
Even though Lief had the Lapis Lazuli to aid his luck, he still did not trust that he could win any of Laughing Jack's fraudulent games on the gambling ship The Lady Luck.
The Lapis Lazuli is the symbol of good fortune and brings good luck to whoever wields it. The effects of the Lapis Lazuli's enhanced luck are hard to clarify, though they are more than likely random occurrences and events. The only time the Lapis Lazuli directly seemed to use its powers was when it caused the Guardian's pets to turn of him. As such, it is the least forward out of all the gems when it comes to displaying its powers.
The Lapis Lazuli also has an affiliation with the Opal, though it is unknown what this affiliation is.
The Lapis Lazuli is given a new power in the anime. Whenever a star shines in the night sky, it banishes all manner of spells. This was used against the sorceress Thaegan during her second attempt to kill the companions.
Before the unification of Deltora, the Lapis Lazuli was kept within a special star-shaped pendant, which was worn by the leader of the Mere at all times.