Dagannoth bones

Dagannoth bones are associated with the Prayer skill. They are dropped by Dagannoth Sentinels, Dagannoth Rex, Dagannoth Prime, and Dagannoth Supreme. Dagannoth bones give 125 Prayer experience when buried, thereby giving the seventh-highest amount of Prayer experience. This is increased to 437.5 experience when using a gilded altar with lit burners or 500 experience when using the ectofuntus.

These bones can be used by wealthier players for power-levelling Prayer, as they can provide around 400,000 Prayer experience per hour.

Dagannoth bones are also a possible reward from the gamble option in Soul Wars. One gamble will give you three to five bones.

Dagannoth bones can also be obtained as a reward from the Dominion Tower.

Cost and XP Analysis
Dagannoth Bones