Travel to King Ranperre's Tomb, and kill Ding Bats at night until one drops some Orcish Mail Scales. Then travel deep into the tomb to find the king's grave. Click on the grave and a cutscene will ensue. Once you have activated the cutscene, and obtained the Orcish scales, return to the gate guard for your reward.
This mission is repeatable. Starting with the second time on the mission, the gate guard will ask you to trade a Bat Fang to complete the mission. It is not necessary to rezone between repetitions.
Exterminate bats from King Ranperre's Tomb, and bring back proof of your deeds.