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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.
Under the reign of the Shadow Lord, the Emerald was given to Gellick for safekeeping. It was however recovered by Lief, Barda and Jasmine, who slew Gellick by forcibly making him drink Dreaming Water and freed the Dread Gnomes from serving him.
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).