Their name came from the fact that they were much older than the people inside the city, the group that would come to be known as the Pubes. The Grays came to Lud as a group of harriers. They coveted the technology and well-being of the Pubes. They were led by the outlaw prince, David Quick.
The Grays eventually established a foothold within the city. They formed their base in the under-works of Lud, unbeknownst to the Pubes. The Grays were gaining the upper hand in their war before Blaine the Mono used nerve gas on the city, which supposedly kills all the residents of Lud.