As people worked the mine, the surrounding landscape was transformed. Grass turned to sand, and sand turned to barren rock. Nearby buildings collapsed. Land sank and water pooled about the mine. Throughout this, Khepry encouraged the miners to continue.
The wasteland is still there on the east bank of the Nile, a few minutes north of Liberty Bridge. It is peppered with dirt mines sunk by players hoping to score their own magnesium mine (futile: the magnesium was concentrated in very tiny cells directly under the mines, not in a normal vein). There are also several Strange Rocks: an unusual concentration of a normally lone object.
This thread on the atitd.net forums contains a number of screenshots of the incident.
The role of Khepry, agent of the Stranger, was played by Devalin.
(See also: The History of Egypt)