Age of Migration

The Age of Migration was the period during which elves of Aen Seidhe cultural group, Feleaorns among those leading them, came to the shores of the Continent on their white ships and landed by Pontar and Yaruga, about two thousand years before the arrival of humans.

Trivia

 * The arrival on the white ships could be reference to J.R.R. Tolkien's Silmarillion. Noldorin elves led by Fëanor arrived in Middle-Earth on white ships which they had seized after slaughtering the Teleri elves during Kinslaying at Alqualondë. After reaching the shores of Beleriand, Fëanor burned the ships to leave his brother's followers behind.
 * On the other hand, Andrzej Sapkowski might not be referring to Tolkien but directly to the Irish mythology from which both Tolkien and Sapkowski took inspiration. The story of the Tuatha Dé Danann people who invaded Ireland from across the sea, burned their ships when they arrived and fought a fierce battle with the then inhabitants was the clear basis for the Exile of the Noldor while aes sídhe (aos sí, "people of the mounds") is the inspiration for Sapkowski's Aen Seidhe, "(people) of the hills".