The Reod was a massive earthquake that created an enormous chasm in the south of Arelon. It altered the landscape to the point where the Aons used by Elantrians, which are based upon the landscape of Arelon, were no longer accurate. This caused all Aons to cease functioning, including the massive Aon Rao created by the city of Elantris and its surrounding cities, preventing the Elantrians from accessing Investiture, and afflicting them with an incomplete Shaod transformation. It was seen by Shu-Keseg and Shu-Dereth as a curse upon the Elantrians for their pagan ways.
Raoden is able to reverse or cure the Reod by adding "the chasm line" to the Aon Rao of Elantris,  which allowed the Dor to flow properly again through the Aons, restoring the Elantrians and the Aons to their former glory.
The earthquake was not natural.
|History of Sel|
|Splintering of Aona and Skai||The Reod||Fall of the Duladel Republic|
|Characters||Raoden · Sarene · Hrathen · Dilaf · Galladon · Eventeo · Kiin · Iadon · Roial|
|Places||Opelon · Arelon · City of Elantris · Duladel · Fjorden · Teod · JinDo · Svorden|
|Magic||AonDor · Aons · Dakhor · ChayShan · Seons · Skaze · The Shaod · Forgery · The Pool|
|Mythology and Lore||Devotion · Dominion · The Dor · The Reod · Shu-Korath · Shu-Dereth · Shu-Keseg|