It could have been the elements themselves, after N’Zoth was defeated the elements became chaotic and refused to answer the calls of the shaman. This was in Shadows Rising. The elements are currently not in harmony but we don’t really know why that is, but we can probably assume that it was the direct result of Azeroth being injured and her possibily having to consume spirit to restore her life force.
Alternatively, if could have been relating to the Old Gods themselves. Cho’gal had shamans under him and they were consuming elements to become “Elemental Ascendants” When the Grimtotem where exiled to Stonetalon Mountains they could have learned this from the Twilight’s Hammer who were also there. During that time Balnazzar may have been masqurading as a Twilight Prophet at the same time. The Twilight’s Hammer were somewhat responsible for Cairne’s death, and they were influencing the events that lead to his death but stoking conflict between the Alliance and Horde. This was in Prelude to Cataclysm.
There’s only two forces on Azeroth who would have ancient information like where the Primal Incarnates are locked up servants of the Titans and servants of the Old Gods.