Ourg bones

Ourg bones are used to train the Prayer skill. When buried, they give 140 Prayer experience. Ourg bones can be obtained by either stealing them from Ogre coffins via the Thieving skill or using keys dropped by Zogres and Skogres on nearby chests.

While training, multiple dragon bones can be bought for the price of one Ourg bone. Just two dragon bones gives 144 experience, which is 4 more experience than a single Ourg bone. If inventory space is an issue, Ourg bones may be a more suitable choice, especially if using on a house altar or the Ectofuntus.

They give 490 prayer experience when used on a gilded altar with both incense burners lit, and 560 prayer experience when used with the Ectofuntus. It is advised to sell Ourg Bones that you get from an Ogre Coffin rather than using them because of their high price/experience.

Trivia

 * Slash Bash, the boss from Zogre Flesh Eaters may very well be an undead Ourg. He drops three Ourg bones.