"We have no other name for them. The Shadows were old when even the
Ancients were young. They battled one another over and over across a
million years. The last great war against the Shadows was ten thousand
years ago. It was the last time the Ancients walked openly among us. The
Shadows were only defeated, not destroyed. A thousand years ago, the
Shadows returned to their places of power, rebuilt them, and began to
stretch forth their hand. Before they could strike, they were defeated by
an alliance of worlds, including the Minbari and the few remaining First
Ones who had not yet passed beyond the Veil."
-- Delenn, "In the Shadow of Z'Ha'Dum"