The Evolution of the Elves

Lolth, who among the elevated Seldarine was most respected by the others, spent time looking beyond Arvandor into the material plane. There she saw how mortals made marks in the world, made changes. She was convinced that the Seldarine could do better then any mortal race, and saw great potential. She convinced many others to abandoned the ever shifting form, and took a singular form. Thus the Elves were born.

The transformation of so many Seldarine, it permanently altered Corellion, and took away the ever shifting form, and even alters the Seldarine who choose not to change. Corellion confronts Lolth, who claims that Corellion had held them back, and that the Elves could only make the best of themselves by separating from Corellion fully.
  While this view was not shared by many, it did spread through some of the others. So angered by the disrespect, Corellion cast these Elves into the Shadowfell, and they became the first Drow. Those whose choose to transform, but longed to remain with Corellion, were cast into the Feywild as mortal Elves. Those who refused Lolth from the beginning remained in Arvandor.