From PathfinderWiki

The Yerbira are a subculture of the Garundi people native to Osirion. These nomadic wanderers are the only human inhabitants of the Osirian Desert outside the two cities cities of Eto and Shiman-Sekh. The Yerbira are famed for their hospitality to desert travelers, but outsiders who abuse their trust face exile in the deep desert or death at the Desert's Mouth. Their cultural laws are extensive but unwritten, passed down orally. The Yerbira are also the only people with knowledge of the desert's few oases.1

Hundreds of Yerbira have been enslaved by Susurex the Crystal King, a blue dragon of the Glazen Sheets.2