Chaosteo is an achievement that requires the player to offer some bones on the Chaos Altar in level 12 Wilderness. Any kind of bones can be used. A spawn of regular bones is located near the Altar.
- This achievement used to be a task prior to the release of the Achievements System on 18 April 2017.
- The name of this achievement is a portmanteau of "Chaos", referring to the Chaos Temple, and "osteo", which is the Ancient Greek word for "bone".