Among The Ruins - Act 4 Side Quest
Start Location: City of Paseron
Quest Location: City of Paseron
Objective: Defeat the groups of Keres in the City of Paseron
Among the Ruins is a quest given to you by Theogenes at the Epirus/City of Paseron zone line. What you need to do for this quest is defeat the groups of Keres enemies with glowing auras around them throughout the town. The locations of each Keres group is shown on my map below as well as what the aura you're looking for appears as.
Once you defeat each group of Keres you'll need to escort the survivors back to the area Theogenes is found. If you get too far away from them they'll stop and not continue towards Theogenes so sometimes you have to baby them and walk with them. Once you've returned all of the survivors back to Theogenes all you need to do is speak with him to complete the quest.