After you're done talking to Xardas, he sends you to go find the Orc Shaman, Ur-Shak. To do this, first leave Xardas's Tower, then head back towards the way you came from, until you come to a mountain with a sloping path leading up.
Follow this path up the mountain until you come to a fortress. Kill the Orc Hunters who come at you, then keep hugging the wall until you come to the courtyard of the ruined citadel. Here you will see Orc Temple Warriors (these guys are tough) attacking another orc, Ur-Shak, the guy you were supposed to find.
Help Ur-Shak take out these Orcs, then talk to him. He will explain the Sleeper (whom he calls "KRUSHAK") to you, and will tell you how to find him, a temple in the Orc City. There are hundreds of orcs here, meaning certain death should you try to approach it, and since Ur-Shak is banished, he cant help you out.
He will explain to you, however, that there is an alternative. You should seek out his friend imprisoned in the mine "Under the village in Hollow". This guy will make you an ULU-MULU, a sign of respect among Orcs. In case you can't figure it out, the village in Hollow is the New Camp, so head over to the Free Mine, and begin your next quest.