Some time before the Clone Wars began, a group of Trandoshan slavers were given entrance into the Kerritamba Village, the home of the Myyydril. Hosdra, a member of the Myyydril tribe, attempted to kill the leader of the Kerritamba Village. As a result, the Myyydril were forced to leave their home. They wandered the forests for days until they came upon the caverns within the Mysess Glade. They constructed a new home within the caverns, and began rebuilding their clan. By 25 BBY, however, the tribe's population began to dwindle for an unknown reason.
It was later discovered that Urnsor'is, sentient parasites, were feeding on the Wookiees. In a desperate attempt for survival, the Myyydril Wookiees fought a vicious battle with the Urnsor'is, but were unable to defeat them. The Poltur Virus soon spread throughout the tribe, further declining their numbers. A female Twi'lek, Yraka Nes, spent many weeks trying to find a cure for the virus, helping the Myyydril remain alive.