Ogres

He nodded to Cho'gall, who called out to the ogres clustered off to one side.

 After a moment of jostling and pushing and grunting one of them stepped forward.

 Cho'gall baked a command and the ogre, shrugging, slouched into the space between the stones. 

It stood at the center of the pentagram and waited, motionless.

 One good thing about ogres was that they could stand still when required. Indeed, when not given an order and not looking for food ogres could stand for hours, as motionless as statues. Gul'dan had often wonderer if they had somehow evolved from rocks. It would explain their dense hides as well as their utter stupidity