Earth giant

Earth giants (also called colossals, and presumably "grom" in Orcish) are a race of giants who lived on Draenor. The earth giants are the ancestors of the magnaron, and by extension the gronn, ogron, and ogres. Whatever they were, the only signs of their passing are the Temples of the Damned built during the Second War, which were all destroyed.

Temple of the Damned
The Temple of the Damned structure was said to be "formed from petrified carcasses of the race of giants that inhabited the Orcish homeworld." These structures would later be used by the Scourge and the Forsaken in the Undercity.

Draenor
The giants were hunted by the Thunderlord clan generations ago. The skeleton of a particularly large one, rumored to be the last of its kind, served as their home in Frostfire Ridge. The largest of these creatures that has ever walked Draenor was rumored to be Gorgrond itself before it died and subsequently turned into the landmass that is there today.

The remains of three other giants, Colossal's Fall, Agurak's Fall, and The Boneslag, can also be found in Frostfire. The skull of one looms over Deadgrin. Another skull can be found far to the east off the coast of Gorgrond, submerged near two small islands that aren't on the map. It has fungus growing out of its eye and mouth. A sixth can be found directly west of Oshu'gun overlooking an Ogre compound.

Appearance
Earth giants likely resembled ogres in the flesh. They had one or two eyes and a horn grew from their heads.

Trivia

 * The earth giants are extinct.