Dagannoth bones are associated with the Prayer skill. They are dropped by Dagannoth Rex, Dagannoth Prime, and Dagannoth Supreme.
Dagannoth bones give 125 Prayer experience when buried. This is increased to 437.5 experience when using a gilded altar with both burners lit or 500 experience when using the ectofuntus.
If players have completed the elite Fremennik Diary, the bones will be dropped as bank notes.