Lightning Returns: Final Fantasy XIII A Final Cure side-quest can be played after Lightning saves the White Chocobo, and after the bird is brought back to Canopus Farms (The Angel of Valhalla main-quest).
Even so, it is a good idea to activate and complete the quest after Lightning’s Chocobo is fully recovered because in A Final Cure you need to move from one sub-zone to another, which means that riding a Chocobo can help you save time.
Regardless on when you decide to start the quest, if you wish to complete it faster you must have a series of materials collected, because the quest-giver, or the client, will ask for them.
The following walkthrough provides the necessary information on where to find the ingredients for Cardesia, when to collect them, and how to complete A Final Cure.
Description: “Lightning meets Cardesia, the apothecary of Jagd Village. She is suffering from a mystery ailment, but worse than the illness itself is the fact that she is unable to brew a cure for a certain patient. Lightning can help, though. She just has to find a red Crimm mushroom and deliver it to Cardesia.”
Location: The Wildlands
Requirements: After main-quest 3-1: The Angel of Valhalla. Start at 8 AM, and finish before 10 PM
Rewards: 1600 Gil, Maximum HP + 80, Magic + 12, Suspicious Mushroom Adornment, Toxic Mushroom Adornment
If you have all materials, the side-quest A Final Cure featured in Lightning Returns: FF XIII can be a short one, but if you don’t, you will have to get them, which means that you will spend some time exploring the Wildlands.
Therefore, make sure you start looking for the following ingredients before activating the quest. Between 6 AM and 6 PM gather Chocoborel Mushrooms.
They are the red mushrooms that grow in the Jagd Forest during the day. After 6 PM the Chocoborel Mushrooms are replaced by Luminous Mushrooms, and you need four of them as well.
Unlike the Chocoborel Mushroom, the Luminous Mushroom is blue and you have to collect it before 6 AM, when the cycle ends, and it transforms into Chocoborel.
For the final step, you have to find a Crimm Mushroom. This mushroom is unique because it grows only in Moogle Village or Rocky Crag. Travel to Moogle Village, north from Jagd Village and look for the Crimm Mushroom in the southern area, which is a dead end.
It is close to a large tree.
Note: While searching for the ingredients, it is a good idea to gather 8 additional Chocoborel Mushrooms and 6 Slug Sweets. The Slug Sweet is dropped by the Rafflesia creature, and you should have at least 6 of them in your inventory.
Rafflesia is a small creature similar to a flower, and it spawns in Jagd Forest. When you have all ingredients, head to Jagd Village. In Jagd Village, you have to find Cardesia, but she opens her stand only at 8 AM.
If the clock shows the correct hour, look for her close to the Outfitters. She has short hair and a brown skirt. Talk to her and make sure you ask Cardesia to prepare a Chocobull potion first (you will need it for a Canvas of Prayers quest in Wildlands).
Give her the 8 Chocoborel Mushrooms and the Slug Sweet and wait for the potion to brew. Now, talk to her again and ask about the Crimm Mushroom, to activate A Final Cure side-quest.
Watch the cutscene, and since you already have all ingredients give them to her, to brew the medicine and finish the side-quest.