A Ritual stone is a stone which is placed in five positions around the Portal at the Clan Camp. It was released on the 1 July 2011. The portal's base, named the unfinished portal, was introduced on the 14 April 2011 along with the Clan camp itself. A total of five clan members are needed to start the creation ritual, after speaking to Avalani.
When trying to do an emote or opening the customisation interface on or around the stones, you will receive the message: These stones are a source of considerable mystical power; don't mess about near them.