Altar tended to by the monk Hamid was located within the lobby area of the Duel Arena and allowed regenerating the Prayer points. Following the removal of the arena it can be found only in its version visited during Our Man in the North quest. Before the rework of the Duel Arena in 2013, an altar was found in the building to the north of it.
Hamid at the Duel Arena altar.
This information has been compiled as part of the update history project. Some updates may not be included - see here for how to help out!