Ranger Captain Venn'ren at Falcon Watch wants you to go to the Great Fissure in Hellfire Peninsula and light the Southern Beacon, Western Beacon and Central Beacon. Return to him with the Lit Torch after you've completed this task.
With the rock flayer population thinned, all that's left is to signal the safe path to our pilgrims. Return to the Great Fissure with this torch and seek the three beacons that mark the path from the east.
Light the three beacons and return to me. Be warned that the beacons will attract any nearby rock flayers when you first light them.