Talk to Magonir to learn of his offer to make you some oil if you bring him the right stones.
Head directly north from Magonir and then west over the bridge and into the Kobold Camp(see map). Work your way around the camp collecting oil stones until you have all 5.
Regardless of whether you have the quest The Kobold Chieftain, you will need to fight the troll boss as he drops one of the oil stones. Return to Magonirfor your reward.
- Note: Temple Guardians appear to be the only class to have two individual class specific quests (neither belonging to a single chain of quests, nor related to their blue chain quest) in the first chapter.