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 or Skogres. Ourg bones give the highest amount of Prayer experience, and can be traded near max price in the Grand Exchange due to high demand.

While training, two dragon bones can also be bought for around 4 000 coins, they will give 144 experience (4 experience more then a single Ourg bone, for a fourth of the price). However, if inventory space is an issue, Ourg bones may be a more suitable choice, especially if using on a house altar or The Ectofuntus, although it is NOT recommended to bury these bones, since they are more valuable than its experience.

They give about 450 prayer experience when used on a gilded altar with incense burners.

Trivia
In the Armies of Gielinor minigame on FunOrb, a battle unit named "Ourg" is available, and its image is that of General Graardor. This has led many players to speculate that General Graardor is an ourg, yet he drops no ourg bones.