I already know the word of Oblivion to release the ring from the arm. Also located the Seal i have to break with the ring in N.W. corner of Hall of Light...but where is that skel. arm? I've as far as i know, cleared out all the accessable maps : (Halls of Stone, Main halls, Deep halls , Lizard Tunnels, Hall of Wizards, Halls of light.)
in the far SE corner of the halls of light is a stairway which leads into a tower of the house of gems. the room of words is in the tower. the arm with the ring is in the room of words on the third level of the tower.