The Fallen Lands: The Ruins of Numinis
The Eladrin that emerged from the Feywild a century ago, were not the same Elves who had fallen into the Feywild in the previous century. The Eladrin, or Anasii Redono, were the descendents of those who originally fell into the Feywild.
The history of what had happened was kept alive through oral tradition and the use of magic to pass memories from child to parent. The knowledge of the cataclysm exists in these scions of the Elves, but any firsthand knowledge is long dead with those who witnessed it. The Eladrin live longer than their Elven cousins, but not as long as their ancient Elven relatives. Two centuries is about average for an Eladrin, many decades longer than their Elven cousins of today.