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Adin knew that he was the one who must fill the medallions in the belt.
Emerald is in need of more information! Emerald is lacking a complete synopsis with every appearance and use of the Emerald in the series.
"The emerald, symbol of honour, dulls in the presence of evil, and when a vow is broken. It is a remedy for sores and ulcers, and an antidote to poison."
— The Belt of Deltora
Along with the other gems of the land, the Emerald was created when, as foretold by the fortune-telling stones of the Torans, fire and water "attached" the land of dragons. The Emerald was the lands gift to the Dread Gnomes.
Adin was able to gain it from the Dread Gnomes, after he saved their leader from being killed by a Green Beast.
The Forests of Silence
Under the reign of the Shadow Lord, the Emerald was given to Gellick for safekeeping. Gellick had it placed on his brow and it remained there for sixteen years, until it was recovered by Lief, Barda and Jasmine, who slew Gellick when Lief threw his water flask into Gellick's mouth thereby forcibly making him drink Dreaming Water. His death simultaneously freed the Dread Gnomes from serving him.
The Emerald dulls in the presence of evil or when a vow is broken. It provides a remedy for sores and ulcers and is an antidote to poison.
During the Toran Plague, many smaller Dread Gnome emeralds were used as a cure.
The Emerald's ability of sensing danger is the only ability shared between two gems, the Ruby being the other one. Also of note is that the Emerald act as an antidote to poison, and the Ruby to snake venom (or venom in general).