The Idol Rock is a natural boulder that lies just south of the cup and ring marked Idol Stone and is a prominent marker visible from many of the other prehistoric sites on this part of the moor.
The rock itself bears no prehistoric markings, although it does seem to bear something akin to a masonic symbol which someone appears to have attempted to grub out at some point (these symbols appear on other rocks elsewhere on the moor).
Nearby prehistoric walling seems to point to this rock being used as a boundary marker and it is clearly visible from the Backstone Circle. West of this point are the living areas of Green Crag and the Backstone Beck Enclosure. East lie the cairns. Maybe this was a division between the lands of the living and the lands of the dead?