They are obtained from Zogre coffins, which will often break lockpicks and decrease players' thieving abilities upon opening using thieving methods. They can also be obtained by looting a zombie impling jar. (Zombie impling require level 87 hunter to catch.) These bones are impractical to train prayer with, as they are significantly more expensive than Frost dragon bones, therefore it is recommended to sell raurg, fayrg, and ourg bones accumulated from ogre coffins.