This broad term encompasses the conflict between the civilized peoples of Men, Halflings, Dwarves and Elves against the races of evil who wished to destroy all that was good and right in the world. These conflicts occurred during the Age of Heroes and ranged from skirmish to full-fledged and total warfare as both sides began to marshal their powers in concerted efforts.
Early on, bands of Lost roamed much like early Men and the Wild Men in the Southern Continent. Violence was a way of life for most people, and the small-scale, random and petty attacks by these creatures were much like those all races employed. Yet, the Lost began to unify, trying to wrest lands like Veridia from the Halflings, or the rich lands of Worthend, or the gold of Indahold, or the magic of Culdonia. Struggles became bitter and for racial survival.
It was this violent focus that drew the civilized races together in the Alliance under Perius, Cep Indahar, Lothar Greatworth, and Merla Underfoot. United, they bore their concerted weight against the army of Lost assembled at the Siegelands and broke them.
The creatures routed in three directions: North — pursued by Lothar and defeated in Sussenia and frozen in the Soundless Brink; South — delivered through Mikk by Merla to a giant melee at Prktakk; and East — squirreling away in the very holdfasts Cep and his Dwarves had vacated to fight the enemy, but were eventually vanquished in a bloody and culturally devastating final battle in the Indahar Mountain Range on Ia Noafa, the holiest of Dwarven days.
The Lost have never again been seen, though Wardens were established as an Order set to protect the frontiers of the civilized world and the vacated holds of the Ancient Clans and still do their duty now generations later.
What they were and why they did what they did are questions lost to the vagueries of history and the fact that Gnomes were not a part of the conflict, and have only been able to piece together bits of the truth from legend and rare, written first-hand accounts. Many claim they were creatures alltogether different from the civilized peoples who remain. Others point out the similarities between the Expansion of Men and their actions — not to mention the untamed bands of violent Wild Men. Whether it was either, or both, we do not know for certain, but are glad that the threat no longer exists and we now live in a time of Pax Omnia