Lightning Returns: Final Fantasy XIII Voices From The Grave is an important side-quest you can play while visiting Luxerion, but only after you complete the fifth main-quest, named Hunter In Light And Shadow.
Voices From The Grave allows you to find a unique item which is required for an additional side-quest, as explained in the following walkthrough.
For this quest you will have to talk to three different NPC, found in specific locations within Luxerion, and then you will have to locate and talk to three ghosts.
Since their locations might be hard to find, using the following guide is imperative if you want to finish the side-quest as fast as possible.
Description: “Residents of Luxerion speak of seeing the ghosts of women, wandering late at night. Lightning should search the city and find out the truth behind the reports.”
Requirements: Complete Main Quest 1-5: Hunter In Light And Shadow. Start after 6 AM
Rewards: 400 Gil, Maximum HP + 40, Strength + 6, Halo
Assuming that by now you know the areas in Luxerion, head to the South Station after 6 AM, and look for the guard that stands south from the Clock Tower.
If you are near the South Station, head NE and you will find the guard near the stairs of the said tower. After you trigger the quest, you will have to find a resident who is located in Pilgrim’s Passage, west from your current location.
The NPC wears a black jacket and it is close to the alley that connects Pilgrim’s Passage and 2nd. Ave. Notice the question marks above his head and make sure you talk to him for additional details regarding the quest.
The second NPC you have to visit is in Plaza of Prayers. Again, from your location head NW, and cross the following areas: 2nd Ave., Idol Ave., 1st Ave., North-South Corridor and Blessed Stroll.
After you descend the stairs in Blessed Stroll you will find a female resident in Plaza Of Prayers. She is wearing a black dress and she also has three question marks above her head.
Talk to her and then head to the North Station. In the Plaza close to the North Station, near Chocolina you should see another woman wearing a white and brown shirt. You will have to talk to her as well. The next step is to find three ghosts, but they appear only after midnight.
When the clock hits 12, or 00:00, return to the Clock Tower and check the area behind the large building. Here you will find a ghost named Zandra.
Listen to her story, and then look for the second one, near the Monument in Sinner’s Corner. Sinner’s Corner is located N from the Residences and it is the same monument where you have completed the Rites For A Goddess main-quest.
Here you will find Myka who will give you the Phantom Rose. Be advised that the item is required to complete the side-quest named A Rose By Any Other Name.
After you take the Phantom Rose, head back to the North Station and you will find the third ghost, Carla, near the central statue where the Inquisitor was located in Whither Faith. Talk to Carla and you will automatically complete the quest and receive all corresponding rewards.
Tip: During this side-quest you should use the Chronostasis to save as much time as possible while moving from one character to another.