During the ordering of Azeroth, the Pantheon bestowed the Pillars of Creation - powerful relics imbued with powerful magic to the titanic keepers to aid them with that colossal task. Ages after the keepers had completed their work, the Pillars would become lost and scattered across the lands of Azeroth.
The Tidestone of Golganneth is one of the titan Pillars of Creation. It was used during the ordering of Azeroth by the titan-forged Keepers to create the rivers and seas of Azeroth. During the third invasion of the Burning Legion, the Tidestone was found in Azsuna under Nar'thalas Academy.

While working on the Tears of Elune appeased my hunger to forge arcane gems, painting the Tidestone of Golganneth delighted me because of the materials involved. I always enjoy working with the elements and water and stone are among my favorite things to texture. I'll be definitely adding one or two more pieces into the Pillars of Creation series, the next addition will most likely be The Hammer of Khaz'Goroth. I hope you like the final outcome!

(description courtesy of Wow Wiki)