The quest begins in the beginning of the fourth chapter `’The Varnhold Vanishing”. Harrim with another dwarf will arrive at the throne room and ask for assistance.

To finish the quest, it is sufficient to see the indicated dwarven fortress (on the lower left of this Temple of the Elk, see screenshot), conquer the adamantine golem and then speak with the dwarves.

Harrim will get the golem’s heart and you’ll be able to decide exactly what to do — ask Harrim to return the thing to Torag or inform him he is not obliged to do anything. The task will be finished, and you’ll get 2400 experience points.