During the time of the Druid Allanon, Heaven's Well was poisoned by the Mord Wraiths, sickening the Silver River and all the lands that depended on it. Jair Ohmsford and Slanter the Gnome journeyed to the top of Heaven's Well, and Jair threw Silver Dust, a magical powder given to him by the King of the Silver River, into the well to cleanse the waters of the poison.
The Croagh is a winding staircase that connects Heaven's Well to the fortress of Graymark down below, and to the Maelmord even further below. After Brin Ohmsford destroyed the Ildatch, the Maelmord could no longer be sustained, and it imploded and sunk back into the earth. The destruction caused the Croagh to collapse, preventing any future access to Heaven's Well but also preventing any future attempts to poison the Silver River. The body of Garet Jax, who died fighting a Jachyra on the Croagh, was lost when the Croagh collapsed, preventing its recovery.