The Descent of the Drow

Corellon interceded in the Crown Wars and cursed the dark elves so that they might never dwell comfortably under the sun. Now finding themselves pained by exposure to daylight, the drow - in a mere two months' time - retreated from the sunlit lands of the world above into the Underdark. They abandoned all loyalty to the elven gods who betrayed and banished them, turning instead to Lolth, the Demon Queen of Spiders, as their patron. Wars soon began between the drow and the underground cities of the dwarves.