FFXIII-2 Fragment Location Guide | (#17) Unio Mystica
Bresha Ruins (5AF) - Retrieve the two capsules
Right before you enter the area with Atlas in the Bresha Ruins (5AF), you'll find a soldier in red looking for two capsules. Both of them can be found near the first set of catacombs, one right to the left of the entrance (revealed with the Moogle Hunt ability) and one right inside and down a set of stairs to the left. Return them to the soldier and get Fragment of Time #17 - Unio Mystica.